Within three years of the last episode Britain's rural rail network had suffered the Beeching cuts and by 1968 main line steam travel had been pensioned off altogether.

It seemed Railway Roundabout, which ran on the BBC Children's Hour slot for nearly 50 episodes, might end up like so many old shows that disappeared into the Missing Believed Wiped black hole in the Beeb's archives.

So the National Railway Museum stepped in to purchase the whole series from its creators John Adams and Patrick Whitehouse in 1980 – only for the film to spend nearly three decades in a storeroom behind the old lecture theatre at the museum.

Finally in January the storeroom was demolished to make way for the NRM's £4m research and archive centre, Search Engine. Bosses realised on clearing the site the film was deteriorating and something had to be done.

Over four years and 47 episodes, containing more than 100 short films, Railway Roundabout had documented the golden age of steam during the late 1950s and early 1960s.

Pre-Beeching, well-staffed branch line stations bedecked with flowers, the heyday of the Brighton Belle and forgotten railway practices such as slip coaches were all captured for posterity before the credits rolled for the last time in 1962.

Now 50 years after the first broadcast the NRM has teamed up with the Yorkshire Film Archive on a major programme of preservation for the Adams and Whitehouse films, safeguarding this historic collection for future generations. Once this has been completed the films will be digitised so they can be available to a whole new generation of railway enthusiasts through Search Engine.

It is planned the public will also be able to view the films via the museum's website, as well as through exhibitions and screenings of the programmes.

Chris Hogg, curator of the film archives at the NRM, said: "This unique collection of films has skilfully captured Britain in the prosperous post-war era, and we are sure there is a whole army of baby boomers who will share an overwhelming sense of nostalgia watching them. It is a real insight into how we used to be."

This will be the first time the whole collection will have been made available for viewing. In the 1990s there was a joint venture between the NRM and Peter Allan Publishing that saw a DVD of edited highlights hit the shelves.

Voiced over by BBC newsreader Peter Wood, the DVD offered a tantalising glimpse of what the film collection had to offer, but Mr Hogg said the entire collection would offer much more, including the rushes, which have never been seen.

Restoring the films to their 1950s glory will be painstaking. At present the original 16mm colour and black and white stock and soundtrack are stored in the temperature and humidity controlled vaults of the Yorkshire Film Archive in York.

Although storing the films under specialist conditions has bought vital time, many early episodes are in desperate need of restoring from the effects of mould, or the dreaded "vinegar syndrome", which attacks the base of the film and eventually renders it unwatchable.

That would have been a sad end for a children's TV gem which started by chance when Whitehouse and Adams met at a preserved railway in Wales and realised their shared passions for railways and film-making.

Mr Adams's neighbour happened to be a high-up in the BBC and the rest was history.