The days of brief encounters with strangers on sleeper trains are numbered because the company that runs the midnight service from London to Cornwall is abolishing shared compartments for passengers travelling alone.

Cary Grant immortalised the romantic potential of sleeper travel in Hitchcock's North by Northwest, which ends with him hoisting Eva Marie Saint up into his couchette as the train plunges into a tunnel.

But now First Great Western has decided to end the practice of putting two people who book separately into the same berth, one on the bottom bunk and the other on top.

A spokesman said: “It is considered more appropriate in the modern age to allow people their privacy. You wouldn't expect to share a hotel room with a stranger and nor should you expect to share a sleeper carriage with someone you don't know.”

Couples will still be able to book a twin berth for £30 each, but all passengers travelling alone will have to pay £40 — or £80 for a return journey — to have a berth to themselves.

First Group, the parent company, is also considering ending the practice of sharing with strangers on its two Scottish sleeper trains, the Highlander and Lowlander, which operate from London Euston.

The move will reduce capacity on the sleepers in a period of rising demand, as more people seek the time-saving benefits of going to sleep in one city and waking up in another.

An existing First Great Western sleeper carriage can accommodate 24 people sharing twin berths but, under the new rules, could provide beds for only 12 people travelling alone.

The explorer Robin HanburyTenison has been travelling on the Cornish sleeper for almost half a century and has often shared a berth with a stranger. On one occasion, the man in the top bunk was a wrestler. “He was a rather large chap and it's a tight squeeze in those compartments. But he was a charming fellow and we did that frightfully British polite thing where one of us went to the all-night bar while the other got ready for bed.

“On other occasions I had some very interesting conversations when sharing with young naval officers joining ships at Plymouth.”

Mr Hanbury-Tenison, from Bodmin, said that he preferred travelling with his wife and booking two single berths next to each other, with the connecting door propped open. “It's well worth the extra £20 to be able to hold hands across the divide.”

While British sleepers have tended to segregate the sexes when booking strangers into shared berths, it is commonplace on the Continent for women to share with men.

Mr Hanbury-Tenison said that this had resulted in some “beautiful relationships”, including the marriage between Nigel Tangye, the writer and wartime pilot, and a young woman who had shared his berth on the Orient Express. “He was returning from Istanbul and in the middle of the night, at Sofia, a pretty young secretary from the British Embassy got on the train. The rest was history.”

Keith Barrow, associate editor of the International Railway Journal, said that sharing with strangers was bearable unless they snored. “It can be difficult to sleep on the sleeper at the best of times and bunking up with a snorer could make it a very long night.”

Andrew Roden, who led a campaign to save the Cornish sleeper when the Government was considering withdrawing its subsidy in 2004, said most people would welcome the new policy.

“It will take away the uncertainty of whether you will have to share with someone you have never met. But fewer berths will be available, which will mean some people have to sit up all night in the seated carriage.”

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