It has been on the cards for some time, but now the end of the wire really is nigh. Tomorrow a switch will be flicked in the City of London that will turn the entire Square Mile into one big Wi-Fi hotspot.

It will mean that the estimated 350,000 City workers will be able to connect to the internet anywhere and at any time. They will be able to send an e-mail while travelling between meetings in a taxi, check out the latest market reports over lunch and conduct a free internet-based Skype phone call to their stockbroker in New York on the way home.

Public Wi-Fi hotspots are nothing new, of course — they have been a fixture of business-class airport lounges and Starbucks coffee houses for several years — but this latest venture is being heralded as the most sophisticated yet and is part of the largest network in Europe. In perhaps the richest square mile in the world, where fortunes are made and lost on future market trends, its significance is hard to miss.

Operated by a company called the Cloud, the new network creates an umbrella of coverage across the City. Conventional Wi-Fi hotspots are constrained to a few hundred feet before the radio waves emitted from the Wi-Fi hub fade and become impossible to pick up.

The Cloud’s system operates by using a network of 127 “nodes” or strategically placed transmitters that pick up the signal from the five main hubs and then bounce it on to the next node, thereby increasing the range. When information is sent the other way — in the form of an e-mail, say — the process is reversed. There is only one physical wire in the network, a cable that connects the main hub to the internet.

“This is Europe’s most advanced Wi-Fi network and it will mean an end to the frustrations of patchy service and broken connections,” says Niall Murphy, co-founder and chief strategy officer of the Cloud. “It will change the way people think about using their laptops or smartphones; for the first time they will be able to receive a fast, reliable internet connection even if they are moving around.”

The revolution isn’t free, however. Subscribers must register with the Cloud in order to gain their user name and password and then pay either £4.50 for an hour’s access (a tariff designed for occasional users) or £12 per month with an annual contract.

The Cloud project is the latest in a series of large-scale Wi-Fi zones that is set to turn Britain into a nation of digital cities. One zone is already up and running in Norfolk, where an area of almost six square miles is covered, including Norwich city centre. In Manchester a partial Wi-Fi network operates in the east of the city and there are plans for a far more substantial zone that will eventually cover 400 square miles of Greater Manchester.

Meanwhile BT claims it is close to completing the first phase of its plan to introduce large Wi-Fi zones to 12 other big cities including Liverpool, Edinburgh, Newcastle, Cardiff and Birmingham.

However, perhaps the most ambitious project of this type is being conducted by the local authority in Warwick. It is about to launch a full trial of an entirely new type of wireless internet technology called WiMax within the next few weeks. The difference is that with a WiMax system the range of the base station is measured in miles, not feet.

To put this in context, by installing just three WiMax base stations the new network will cover “all of Warwick, most of Leamington, and bits of the nearby rural areas”, says Chris Elliott, chief executive of Warwick district council. Should the trial prove successful, and if other areas take it up, it could pave the way for the whole of Britain to be covered.

So why the sudden rush for Wi-Fi and is it a good thing? In the case of companies such as the Cloud and BT it is a business venture: subscribers are charged for using the service. In Norfolk and east Manchester the projects are all largely funded by local authorities in order to offer universal internet access. Not only does this allow everyone a share in the knowledge revolution, it can also play a part in regenerating run-down areas of a city by attracting businesses and visitors who know that they can have instant internet access.

Councils also claim it saves them money by allowing greater working flexibility. In Warwick the council anticipates substantial savings by removing the need for employees to keep returning to the office or making paid phone calls. Instead they can communicate by e-mail or Voip (voice over internet protocol) calls.

Not everyone is welcoming the unstoppable spread of Wi-Fi, however. Traditional mobile phone companies are fearful of a technology that offers free phone calls as well as services that phone companies hoped to charge a heftier premium for, such as video calling and picture messaging. Mobile operators including Vodafone and Orange are attempting to fight back by offering faster speeds and better tariffs for 3G phones (which allow internet access when coupled with a laptop).

Vast Wi-Fi networks have also raised some security fears. Last week, in one of the first cases of its kind in this country, West Mercia police cautioned two people they had previously arrested for “piggybacking” on other people’s private Wi-Fi networks. Although the incident wasn’t associated with large Wi-Fi zones, it highlights growing concern about a new breed of cyber criminals and the relative ease with which they can access a Wi-Fi network.

“The casual use of these large networks for sending e-mails, for example, is like sending a postcard — anyone can read it,” says Peter Wood of the British Computer Society. “City workers would be crazy to be pinging around important information on a public network without taking serious precautions.”

And even if precautions are taken, hackers can still bypass firewalls or even go to the lengths of setting up a so-called “evil twin” — a dummy network that fools unsuspecting consumers into thinking they are logging onto a legitimate Wi-Fi service when they are signing on to a rogue one.

The Cloud and BT claim that unlike many free Wi-Fi setups their networks are secure because anyone logging in needs a unique user name and password. Nevertheless, users are advised to scramble sensitive information. “We don’t operate over-the-air encryption software so we recommend that customers do,” said a spokesman for the Cloud.

Probably the biggest question mark over the future of commercial Wi-Fi zones is how much they will cost. While BT and the Cloud charge subscribers to make use of the service, many of the council-run schemes are free. In fact only a mile or two from the City, in Islington, north London, there is already a free Wi-Fi zone up and running operated by a company called Cityspace. The firm also runs a free network in Bristol, which it claims is attracting large numbers of users.

BT, however, claims its subscribers will receive a quicker and more consistent service that justifies the price. “We don’t believe in free,” says Steve Andrews of BT. “Free is destined to failure — somebody has to pay for it all.”

The Cloud, which already operates around 7,000 smaller Wi-Fi hotspots across Britain, agrees. “The City of London is not exactly populated with people who need social support. They want the fastest network possible and are prepared to pay for it,” says Murphy. Even so, he accepts that some tariffs may have to go down as competition increases: “I’m no more a fan of paying £5 for 60 minutes of Wi-Fi than you are.”

HOW TO GET WI-FI ACCESS

- First, you will need a laptop or a smartphone with either a Wi-Fi receiver built-in or a plug-in card

- To find your nearest Wi-Fi hotspot check out websites such as www.jiwire.com/search-hotspot-locations.htm. Free alternatives can be found at www.free-hotspot.com

- To access paid-for Wi-Fi such as the Cloud you must buy air-time vouchers or set up an account (www.thecloud.net)

- Some broadband ISPs, such as BT, bundle free Wi-Fi hotspot access for use in a variety of locations, and many mobile phone networks offer monthly Wi-Fi tariffs

- Public Wi-Fi hotspots are less secure than a home network that has been properly encrypted. Before using a public Wi-Fi network, turn off all file-sharing options in Windows and password-protect important files

- Never conduct online banking, credit-card transactions, or send e-mails at a public hotspot unless these are encrypted with software such as PGP Desktop (£76 from www.pgp.com). Ensure a software firewall in your laptop is turned on, such as ZoneAlarm (free at www.zonealarm.com)