By Rory Cellan-Jones
Technology correspondent, BBC News
The City of London has fired up its first mesh wi-fi network, promising net access from just about anywhere in the Square Mile.
The mesh network covers London's financial district
The area in London is not just Europe's leading financial centre - it is said to be the continent's most advanced wireless network too.
That is the claim made by the network's creator The Cloud and by the City of London Corporation which has backed it.
There are 127 nodes on lamp posts giving access to 350,000 people.
The City of London Corporation believes it will be invaluable to traders, bankers and brokers who want access to their data when they are on the move - or out at lunch.
"Every second counts when you are doing deals," explains Simon McGinn from the Corporation.
But unlike some examples of municipal wi-fi, this network will not be free. It is available to a variety of providers who will charge customers a range of fees to log on.
The network covers 95% of the City's streets, though it is does not reach right across private land like the Broadgate development and the Inns of Court.
The Cloud - which operates wi-fi zones across Europe - says advanced mesh technology means users will be able to move from one node to another without losing internet access.
I climbed into one of the cycle rickshaws which now crisscross the City and tried the network out. I picked up the signal pretty easily and, despite a few hiccups, stayed logged on from Finsbury Circus to Smithfield.
But is there really that much demand for open-air surfing? After all, staring at a laptop screen in the sunshine is not a great experience - especially in an area where so many cafes have wi-fi access.
The network's backers think one of the big attractions will be the ability to use wi-fi enabled phones to make cheap calls using Skype or other internet telephony services.
It's hard to see why well-paid City workers would bother with the extra effort needed to make a wi-fi call - but the City of London Corporation believes it will prove attractive to migrant workers on construction sites.
Public wi-fi networks, free and paid-for, are spreading quickly, but there are mixed reports on just how much they are being used. Some believe the more advanced Wimax technology is the real answer to open-air internet access.
So the City of London's network will provide a major test of whether the public really wants to surf on the move - and whether there is any money to be made from it.