The first airport-style security for rail passengers began operating on12 January at Paddington station in London.

Passengers will be required to walk through a scanner and could also be subject to a personal search.

The added security is part of a four-week trial of scanners and equipment on Paddington’s Heathrow Express platforms to test methods of improving security at railway stations.

It is understood that further trials could be launched soon on the London Underground and other railway stations in the capital. A Downing Street spokesperson has denied the increased security measures are specifically in response to the terror attacks of 7 July last year, where 52 people were killed after four suicide terrorists used the mainline rail network to transport their bombs.

The spokesperson said that, while 7 July had “changed the picture” in terms of security, the Paddington station pilot was mainly about testing the equipment and was not a response to a specific security threat.

Visit London’s Ken Kelling said that they did not expect the security trial of scanners at Paddington to have an adverse effect on the capital’s visitor influx. He said: “Participation in the trials is on a voluntary basis, and designed not to disrupt passengers’ travel plans.

“Visitors from around the world are increasingly used to such security measures. We wouldn’t think this trial will put them off coming to London – in fact many people find it reassuring that this kind of planning is being taken very seriously.”

Kurt Janson of the Tourism Alliance added: "The Tourism Alliance is supportive of moves to increase security at Paddington. It is important to show visitors to Britain that we take their protection very seriously. Britain's police force is admired around the world and, rather than deter visitors, this move will provide reassurance for people visiting from overseas."

Approximately three million passengers are carried every day on the London Underground alone, while the railway system carries one billion passengers a year, using 11,000 miles of track. Details: www.number10.gov.uk