Just in time for summer, the Square Mile today became one big hot spot, as Europe’s most advanced wi-fi network was switched on across the City of London.

The system, run by The Cloud, the wireless broadband provider, has been designed to give 350,000 workers reliable internet access away from their offices via laptops, PDAs and smartphones. It echoes other schemes bent on making internet access ubiquitous, championed by groups such as Google in San Francisco.

Access to what is being billed as the “densest, most comprehensive city-wide wi-fi network in Europe” will be free for the next month. After that, users will be charged £11.99 a month for “all you can eat” access to broadband speeds of up to 8MBs, or £4.50 for an hour.

The service will be delivered through a “mobile broadband mesh” formed of 127 “nodes” – gadgets that look like small black beer barrels attached to strategically placed lampposts.

In theory, brokers will be able to log-on to check stock prices from the back of their cabs; lawyers can call clients around the world for next to nothing using internet telephony services such as Skype; and analysts will be able to e-mail each other spreadsheets while they lounge in the sun.

After a year of trials, however, the reality is about to be tested in earnest. The City’s architecture could yet prove problematic, with anecdotal reports suggesting that the service can be patchy when used very close to large glass buildings – of which there are a few in the City.

There are also security concerns. The British Computer Society has given warning that “City workers would be crazy to be pinging around important information on a public network without taking serious precautions.”

The move was all but inevitable, however, as London competes tooth and nail with rival financial centres such as New York and Frankfurt.

Michael Snyder, the chairman of the City of London's policy committee, said: "The Square Mile is a fast-moving, dynamic environment and we are responding to the increasing time pressures faced by City workers by providing the technology for them to stay up to date, wherever they are in the City."

Large-scale wi-fi networks appear set to become a standard feature of big cities in the next few years. Eight in the UK, including Birmingham, Cardiff and Glasgow, are already working with BT’s Wireless Cities programme, under which BT will roll out paid-for wi-fi services.

The are also plans for large municipal free wi-fi projects – including one to cover all of Greater Manchester – inspired by similar programmes in San Francisco, Seattle and Amsterdam, which provide free internet access across large urban areas.

Milton Keynes, Norwich and Leicester Square in London have free wi-fi systems in place funded through public money and commercial sponsors. Warwick. meanwhile, is pioneering a rival system called WiMax, which is already used in pilot schemes to provide wireless internet access to huge swaths of the Amazon rainforest.

Meanwhile, City workers reticent to join the always-on culture may want to consider hunkering down during sunny lunchtimes in one of the privately owned areas of the Square Mile, such as Finsbury Square, which will not be covered by the City service.

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