In a curious deal inked last week, BT has joined forces with Spanish social wifi outfit FON.

By social wifi, I mean that you share a chunk of your wifi connection with strangers and get yourself free access through other members’ routers. If enough people do this, then the globe theoretically gets covered with ‘free’ wifi access for people on the move.

All the blurb talks about giving up a small percentage of your broadband connection. The small print says this is 512kbps. It wasn’t so long ago that this was the maximum speed of a connection.

Anyway, looking more closely, you find that Skype and Google, as well as BT, are putting money into FON. I seem to remember that BT floated off its mobile operation, O2. Could this be a sneaky way back in to mobile telephony? Skype provides free calls over the internet. FON gives free access to the internet. Put two and two together…

But don’t get excited. Mobile phone coverage is hugely better than FON coverage, even with BT throwing in some of its Openzone hotspots. Not all of them though, it’s reserving some as Premium hotspots.

I checked out a few potential locations. All you have to do is throw a postcode into the hotspot finder. First of all, where I live - in a kind of outer London village - there’s nothing. You have to sit in someone’s front garden a couple of miles away. But it’s early days. The service only kicked off last Thursday.

Central London shows a lot more hotspots. But where do business people really want hotspots and where do they pay through the nose for them? Airports. Slap in the Heathrow postcode, TW5, and get nothing. Oh dear. But Terminal One sports a couple of Openzones. I guess they’re denoted as ‘premium’ by BT.

In due course, the density of free access points will increase. It will potentially grow faster than any kind of official wifi rollout. It is claimed to be secure because it uses an encrypted ‘visitor’ channel quite separate from your normal wifi connection. If you are a BT customer, it’s built in to your router. If you’re not, you buy a ‘cheap’ router which can split the signal. It costs between 35 and 45 Euros depending on model.

If you do decide to join the FON community, you would do well to check with your ISP. Some, in fact most, don’t like you sharing your bandwidth with others. BT, of course, is one of the exceptions.