We spent a day traipsing around London with Broadband Genie to find out whether public Wi-Fi hotspots offer sufficient coverage that you don't need a cellular connection. How good is public Wi-Fi? Read on to find out. (Visit Broadband Advisor for more.)

It started with a claim. A bold claim. During a conversation about connectivity on the move an executive at a leading public Wi-Fi provider told us cellular connectivity was no longer important. Expensive and slow, yes, but not required in most user cases, he said. This was because, he claimed, you can always find a public Wi-Fi network when you need to get online.

Such a claim requires testing, and testing is what we do here at PC Advisor.

We took to the streets to find out just how much connectivity there is to be found. We paired up with our friends at Broadband Genie and signed up to the three major public Wi-Fi networks, BT Wi-fi, O2 and The Cloud. Armed only with a laptop, we sent five testers on to the streets of London, setting them a series of timed web-based challenges, each to be completed at the same time in the same place.

The five contenders included three testers who were allowed only to use their chosen public Wi-Fi network, BT Wi-fi, O2 or The Cloud. We also had a wildcard tester who was signed up to no accounts, but able to use any public Wi-Fi network that didn't require direct payment. As a control we had one tester using 3G, with a dongle from Three (the winner of our recent best mobile network group test).

Some caveats: we tested in central London, which is unusually well covered by public Wi-Fi. This was to give the testers the best possible chance of success and because, well, we're based in London. Experience may differ in your area, although you'll see as we go along that the types of places in which you can get online can be found in most towns and cities. The rural experience is, of course, very different.

This was not a scientific test. To an extent it required ingenuity and flexibility on the part of the individual tester. Consider this more of an anecdotal piece: in part we wanted to test just how much thought was required to find a usable connection. The user experience is an important part of all consumer tech, after all.

It's unlikely that in real life a customer of, say, The Cloud would ignore a free BT connection and cast aside a working 3G network to find a Cloud hotspot. In reality, we would all take the most convenient option to get online, provided it was fit for purpose and unlikely to cost us more than the service for which we'd already paid. See also: The UK's best mobile networks revealed: mobile broadband group test.

Public Wi-Fi hotspot

How good is public Wi-Fi? How we tested

For each task each tester could use only the Wi-Fi service they'd been allocated, with the exception of the wildcard tester who could use only free public Wi-Fi. All the contenders started in the same place at the same time, then had to find the nearest wireless connection to complete the task we set.

It wasn't a competition as such, but an experiment to see how feasible it is to rely only on public internet. The contenders had 10 minutes to complete each task. If they couldn't do so, it was considered a failure.

The testers knew in advance which network was theirs to test, so they could research which third-party stores, bars and restaurants would likely offer a connection. They did not know the location or content of the tests, however, so couldn't plan ahead. See also: Android vs iPhone vs Windows Phone vs BlackBerry: which is the best phone to use on the move?

Public Wi-fi test 1. Read a book at the British Library

Starting from the yard outside the British Library, we asked our testers to find a web connection, search for the Project Gutenberg website and find Gulliver's Travels by Jonathan Swift. They then had to download and open the ePub (with images) file, and note the time in which they completed the task, and the location of the connection used.

Our O2 tester had previously signed up to O2 Wi-Fi and downloaded the app to their smartphone. Thus it was easy to find a hotspot in a nearby coffee shop. However, it was a lengthy and difficult process to get online. By the time the laptop was connected they had ran out of time to carry out the task.

Our BT tester had a similar experience with a better outcome. They thought the BT signup process could be more streamlined, with less personal data required. However, they were able to quickly and easily download the book in the public lobby of a local hotel.

Our The Cloud tester found several hotspots close by, including three just over the road. An initial attempt in a Pret A Manger was unsuccessful as the connection was saturated by the lunchtime rush. Our intrepid hack popped next door to a Pizza Express and managed to very quickly download the e-book while standing outside.

There they shared a connection with our wildcard, also nicking Wi-Fi without paying for even some dough balls. Our wildcard initially headed to Starbucks, but it being a café near two major rail stations found it rammed with customers. Our tester could get a flat white and the promise of own-brand internet access, but not a seat. And web access turned out to be false promise, as they couldn't get past the branded pop-up window.

Our wildcard tester ultimately downloaded the book from the same The Cloud network as our The Cloud specialist. Lesson learned: restaurants have better internet access than coffee shops, even if you're next door in the latter.

The 3G control downloaded the book in a couple of minutes without moving from the start point. (See also: What's the best mobile network? UK mobile broadband tested.)

Public Wi-fi test 2. Plan your route on the Tube

The TubeWe then descended to the platform at King's Cross Underground Station, and asked our testers to navigate to tfl.gov.uk and use the journey planner to plan a route to St Paul's. We were miles below ground level so the 3G dongle was a washout.

O2 supports Wi-Fi on the tube, via Virgin Media. On the underground platform our O2 tester was able to sign into the Virgin Media Wi-Fi for free with their O2 credentials. They then hopped online and planned the journey in around three minutes. Neither BT nor The Cloud could match this.

Initially things went well for our wildcard tester. As Virgin Media's Wi-Fi was easily accessible they could either pay for a day's access or log in via EE, Vodafone or – although a nearly hidden option – 02.

We wouldn't let them pay any cash, but as an O2 mobile customer we let them plump for this. Our tester entered their mobile number and was told to expect a text with further instructions. A text they wouldn't receive until we resurfaced at St Paul's Station. So near, and yet so far.

Public Wi-fi test 3. Learn history at St Paul's

St PaulsWe travelled down to the front of St Paul's Cathedral, where we asked our testers to find a web connection and search for a story on the BBC website entitled How St Paul's Cathedral survived the Blitz. Then we asked them to save the main image to the desktop. Needless to say finding the image was no problem for our 3G control, although it did take a minute or two to download.

Our O2 tester had a better time. Their laptop automatically connected to an O2 hotspot at Yo Sushi, without them having to move. They were able to find the BBC news article and download the image in about two minutes.

Our BT tester could only envy such success. They found a BT Openzone at a Starbucks, and even managed to surf to the BBC home page on another overloaded connection. However, when they could surf no further they closed the browser to start again and found they couldn't reconnect.

Our The Cloud tester found numerous hotspots within a close proximity. Like O2 they were able to get a reasonably good connection sitting on the steps of St Paul's.

There was an odd issue with Chrome, which threw up a strange login screen, and the usual Sky ID did not work. But a quick switch to Firefox and our tester was able to connect. However, they then had to re-register the laptop with The Cloud and this part of the process would not finish, leaving our tester hanging on the device management screen.

A quick switch to a smartphone allowed the The Cloud tester to complete the task in the time allotted. So the connectivity was good, but the user experience not. This was not an unfamiliar occurrence.

And what became of our wildcard tester? Like the other testers they could see many networks, and five were accessible from where they were standing. They simply sat down on the steps and logged on. They also found Starbucks' network overloaded with PowerPoint pitch presentations attached to pressing emails and Russian hair braiding videos from YouTube, but Yo Sushi's Wi-Fi was wide open and the task was completed in no time.

Public Wi-fi test 4. Find out what's on at Tate Modern

TATE MODERNAfter a brisk trot across the river (using a bridge) we found ourselves at the front of the Tate Modern gallery. The task here was simple: find a web connection, open the Tate Modern website and find the What's On page. It should have been simple, and it was for the 3G control test.

It was relatively simple for our O2 tester, too. Using the O2 app they located the nearest hotspot – a five-minute walk away at a local pub. The laptop automatically connected before our tester had even ordered a drink.

Our BT tester had a much tougher time. Right outside the Tate several different, but apparently usable, networks appeared: BT Wi-fi, BT Wi-fi with Fon and BT Openzone. Our tester opened their browser and was taken to a BT wireless page to log in. However, they couldn't sign into their account because it was the wrong kind of BT Wi-fi. A hop around the corner to a – yes – Starbucks solved this problem, but the sheer variety of 'BT' networks was baffling. Another example of the importance of the user experience as well as the connectivity.

Still, that experience beat The Cloud tester's. The smartphone app displayed a few hotspots in the area that seemed to be a short distance away, but our tester was not able to find them within the time limit. Fail.

Meanwhile, as their colleagues charged off in different directions to find their individual networks, our wildcard tester had cannily noticed that the Tate has its own Wi-Fi, so waited smugly for them to depart and logged on from the café (you have to drink a lot of coffee to surf on the move). Unfortunately, they couldn't connect, so our wildcard tester drank up and moved to a different floor. Again, no luck. There was time for only one more try but, again, nothing. Another fail.

NEXT PAGE: we watch the South Bank Show on the south bank of the river...

Public Wi-fi test 5. Watch the South Bank Show at the South Bank Centre

Starting from outside the Royal Festival Hall on the South Bank, we asked our testers to find a web connection and navigate to YouTube. They then had to find and watch a clip called ‘The South Bank Show Opening'. To pass the test they had to watch the entire clip, something that proved beyond our 3G control. Public Wi-Fi fared much better.

Our O2 tester's laptop again automatically connected to a hotspot, a Yo Sushi network. They were able to load and watch the YouTube video within a minute of taking the laptop out of its bag.

Our BT tester had to enter his login details again, but also quickly loaded and watched the video.

With The Cloud we also found a strong signal even sitting outside. Once again, however, our tester had to register his laptop with The Cloud. After a couple of aborted attempts where it seemed to hang at the final step this was successful. Once that was done the video loaded right away.

Interestingly, our wildcard had better luck with the same network. Their laptop instantly logged on to The Cloud's Wi-Fi, remembering the login from Pizza Express.

SOUTH BANK CENTRE

Public Wi-fi test 6. Watch ITV at the London Eye

LONDON EYEWe nipped down the river, stopping just outside the London Eye. There our intrepid testers had to find a web connection, head to the ITV website, then find and watch the opening credits of the most recent episode of 'Coronation Street'. The 3G control test got as far as the web page but was unable to stream, and the Wi-Fi networks proved similarly reticent.

Our O2 tester's smartphone app showed a hotspot at McDonalds, but they couldn't find the network. Fail. Our BT Wi-fi tester had a marginally better experience, finding a BT Openzone, and even navigating to Corrie before the Wi-Fi dipped out. Fail. There's a Cloud hotspot right next to the London Eye, but it seemed far too busy to allow our tester to finish the task. They found the page, but the video wouldn't start. Fail.

Our wildcard tester found another network in the Namco games centre, but couldn't stream the clip. So none of us got to watch 'Coronation Street'. Gutted.

Public Wi-fi test 7. Watch Wills and Kate get wed at Westminster Abbey

Having failed to indulge our taste in high culture, we headed back across the river to Westminster Abbey to find some high society. The task here was to find a connection and watch, via YouTube, the official video of last year's Royal Wedding. To complete the task our testers had only to get the video playing.

Our 3G test did manage this, although the clip was a little jumpy. Not so for the O2 public Wi-Fi. Again, our tester's laptop automatically connected to a hotspot, at Parliament Square, and the clip quickly loaded and smoothly played.

The BT Wi-fi experience was not so good. Despite BT's map suggesting that Parliament Square is one big BT hotspot, our tester could find no connectivity. The Cloud at least spared us the dashed hopes. The Cloud was not available here, although the app did show several hotspots clustered at nearby streets.

Our wildcard tester took advantage of the 02 Wi-Fi account he had set up earlier.

Public Wi-fi test 8. Post a selfie at the National Portrait Gallery

As our test drew toward a close we decided to capture the occasion for posterity, heading to Trafalgar Square and asking our testers to post self-portraits on Twitter, using public Wi-Fi to get online with their smartphones.

This was not a problem for the 3G control test, as it is the sort of thing for which you would naturally use cellular connectivity.

But the public Wi-Fi users struggled.

Our O2 user was connected, but was unable to upload the photo to Twitter or even browse the web. The experience was better with BT, but our tester had similar issues. His phone connected okay, but there were problems tweeting. He had to go into the browser and enter login details, then return to the Twitter app. Our wildcard tester used the O2 hotspot with no problems, however.

The Cloud experience was similar to that of the previous test. Our tester could find no signal in the square itself, but there was some connectivity at nearby bars and restaurants.

Public Wi-fi test 9. Find the way to your hotel from the Tube

We finished our test by using our connections to find our way from Marble Arch tube station to our hotel, using Google Maps.

The 3G control worked fine, if a little slowly. And our O2 tester's laptop had no problems automatically connecting; they were quickly able to plan the route to the hotel. That's the route down which our wildcard tester also travelled, with similar success.

The BT Wi-fi test wasn't so good: our tester signed in just outside the station, but the connection initially failed despite what appeared to be a strong signal. After a few minutes it began working and they were able to complete the task.

We had a better time with The Cloud. Here we picked up a decent signal just outside the tube station thanks to a nearby coffee shop and rapidly found directions on Google Maps.

How good is public Wi-Fi? Verdict

So is it true that we no longer require cellular data? Will public Wi-Fi suffice? We'd say not. There was at least one task that none of the public Wi-fi users could complete, and we never failed to get online using cellular data. But we were generally impressed by the public Wi-Fi networks. In central London they are very common, although there is an element of feast or famine. In some areas we could choose from multiple networks; in others we had to move to get online.

One regular complaint was the poor customer experience. Our test was slightly false because in most usage scenarios consumers would be set up to use their chosen network in advance. But there may be some work required on the user interface and mobile app side of things.

Nonetheless, we were pleasantly surprised at the ubiquity and quality of public Wi-Fi. In general it is super-cheap or free and, as such, it is much cheaper and quicker than is cellular data. The networks themselves all performed at a similar level – no single one stood out.

When you set out on a journey for which you will require connectivity, we recommend signing up to public Wi-Fi, but also taking along a good 3G-enabled device.

How good is O2 public Wi-Fi?

"O2 Wi-Fi was generally good. Setup online was easy, but adding my laptop as a second device proved a pain. From then on, when in range both my smartphone and laptop connected to networks and the performance was great, just like being at home.

"The landing page glitch was the main problem I found. Coverage was consistently good in London, although when you're not near a hotspot the smartphone app and mobile data is required to find one." Chris Martin

How good is BT Wi-fi public Wi-Fi?

"I found I had to log in too many times, and there were too many different options: BT Wi-fi, BT Wi-fi with Fon, BT Openzone and BT Openzone Starbucks (the Starbucks option was generally best). As a paid-up customer of BT Wi-fi, I think it should be much simpler.

"Many of the hotspots seemed to be outside-only, which wasn't great on a wet, windy afternoon in London, but useful if you are on the hoof.

"We weren't impressed with the apps – the hotspot map wasn't very good, for instance. And, on a laptop, it seemed as though you couldn't go back to BT page if you'd already been there but failed to login. It would open the first time you opened the browser, but if you didn't sign in and restarted the browser it disappeared.

"In general, then, connectivity was okay, but the user experience wasn't great." Peter Ames

How good it The Cloud (Sky) public Wi-Fi?

"I had expected this to go a lot smoother, since The Cloud boasts of thousands of hotspots around the country. Frequently, though, it seemed that major areas were bereft of connectivity, even when other networks were available.

"The Cloud generally was nearby, but this almost always involved walking to a café or restaurant. That's fine if it's not raining and you can stand outside, or get away with sitting in there while checking your email, but not many restaurants will let you take up a seat without paying for something.

"The Cloud smartphone app proved useful for quickly locating hotspots and seemed generally accurate. One oddity of The Cloud network highlighted by the app is the clustering of the connections – you can walk for ages and not find anything, then there will be three or four in a very small area, often in adjoining coffee shops. It would be more useful if they were spread out, although it does mean that if the place you're in is very busy you can try next door's connection.

"All devices should be registered with The Cloud ahead of time as this part of the process can be painful on a busy connection. The device- management screen can take a little while to load up and behaved strangely when the link was slow. Once that was done, though, both my smartphone and laptop instantly latched on to the hotspots instantly without any further fuss." Matt Powell

How does 3G compare to public Wi-Fi?

"We could get online on every occasion – as you'd expect in London. But it's not all perfect. Streaming video was always a trial. In fact, we couldn't get any of the videos to play properly. And downloading files on even a robust 3G connection can take a while. And that's before you factor in cost." Matt Egan

And what of our wild card?

"Overall, I probably had the easiest time of all. No network is everywhere but, in central London at least, you're usually near some kind of wireless hotspot you can get on to for free. Unless you're an 02 customer on a tube platform, at which point you're just frustrated." Neil Bennett