Danger threatens the bespectacled brethren in their anoraks, who hang about on railway platforms with their spiral-back notebooks and sandwiches in polythene bags. The train company National Express is clamping down on people boarding trains without tickets, which union leaders say means trainspotters will be barred from their favourite platforms.

But the company claimed yesterday that the clampdown need not affect trainspotters, who will be able to use platform tickets to pursue their hobby. Gerry Doherty, the general secretary of the Transport Salaried Staff Association (TSSA), pointed out that platform tickets had not been offered for sale since railways were privatised more than 10 years ago.

He accused National Express of having no respect for a tradition almost as old as the railways. "Sir John Betjeman will be turning in his grave," he said. "It means that the barbarians have finally taken over the industry. Only people with no sense of history would commit such an act of mindless vandalism.

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"Young trainspotters have been with us since Victorian times. Now National Express are saying they should be banned because they are a nuisance. These people know the price of everything and the value of nothing. They do not respect the industry or its values. They should go back to running buses.

"One of National Express's managers actually told one of our reps that trainspotters were now a security issue. Do they think a 10-year-old boy with a pencil and notebook is in possession of a dangerous weapon? You do wonder what planet these people are on sometimes."

The TSSA, which represents 20,000 clerical and professional staff on the railways, has promised to contact the chief constable of the British Transport Police to ask him to enforce guidelines introduced during the privatisation that guaranteed trainspotters access to railway stations.

National Express said it was obliged to tackle the problem of people travelling without paying, and that one of the most effective deterrents is electronic gates which prevent people without tickets from getting on to the platform.

A spokesman said: "This is more mischief-making by the unions. Platform passes will be issued to people, including our trainspotters, who wish to go on to the platforms but aren't travelling. Gating is part of a contractual agreement with the Government. Gating will prevent fraudulent ticketless travel and protect revenue. This substantial lost revenue will be channelled back into the rail industry including investment in enhanced facilities."

Well-known former trainspotters include Michael Palin, the former chancellor Kenneth Clarke, W H Auden, who in 1935 wrote the poem Night Train, and Betjeman, whose bronze statue adorns St Pancras station, which he saved from demolition.