Last month we wrote that FT.com’s subscription revenue was on course to overtake its ad-based revenue in 2012, with Rob Grimshaw, Managing Director of FT.com, adding that mobile will be the Financial Times’ main channel for distributing news within ‘three to four years’.

Today the Guardian reports that the FT’s HTML5 Web app has attracted more than 2m users since it launched last summer, in the wake of rules imposed by Apple in relation to iOS apps.

To summarise, the FT had expressed concerns about the lack of data Apple made available of user activity from the App Store. It was this concern that formed the basis of the new Web app, though the 30% cut that Apple takes will have played a part in the move too. The FT said at the time:

“We have launched a new, faster, more complete app for the iPad and iPhone which is available via your browser rather than from an app store. We’re encouraging our readers to switch immediately to the new FT web app, as many new features and sections will be added over the coming weeks. Make sure you don’t miss out on these updates. Go to app.ft.com on your iPad or iPhone.”

Two weeks after it launched on June 7, it was already being accessed by 200,000 people, and we speculated at the time that if the FT could succeed with its new approach, it could help drive other news publishers towards HTML 5 over native apps.

The FT site sits partially behind a paywall, and whilst you can register for free to read up to eight articles per 30 days, £5.19 per week gets you nearly full access to all its digital content (including mobile Web apps), and for £6.79 a week, you get a few added extras on top.

As noted in the Guardian today, the FT now says that its Web app drives 12% of FT.com subscriptions and 19% of traffic, and in the last six months, smartphone users have grown my more than half (52%), with tablet readers up by 49%.

So ten months after launch, the FT is showing that Web apps could be the future over native apps, and there’s certainly good reason to be thinking in terms of HTML 5. The costs of developing for multiple mobile platforms can be prohibitively expensive at a time when many publications are looking to streamline and cut back, and being able to scale across all devices with ease will likely appeal to more and more publishers.