FILM buffs and York historians could end up with a real blast from the past when experts try to restore a key piece of the city’s history.

For the ageing Rowntree advert they want to work on is so delicate that, if it goes wrong, it could literally blow up in their faces.

Yorkshire Film Archive and Nestlé are hoping to recondition an old advert starring Rowntree’s iconic marketing character, Mr York of York, Yorks.

It is believed to have been the first advert to feature both sound and moving pictures, but it is on nitrate film, which can potentially dissolve into nitro-glycerine and explode like a bomb.

The seven-minute cartoon about Mr York was an advert for “Plain York” chocolate – the predecessor to what is now the Yorkie bar.

It is one of a number of films to be restored, and Nestlé hope the films can be shared with staff and the public once the restoration is complete.

Alex Hutchinson, heritage assistant at Nestlé Confectionery UK in York, said: “The ‘Plain Mr York’ film is part of a collection of Nestlé Confectionery films being restored by the Yorkshire Film Archive.

“The film is of huge historical importance. It is difficult for most of us to imagine going to the cinema and seeing an advert that lasts over seven minutes, but to its first audience it will have been a real novelty – I bet they were glued to their seats!

“Very little film footage from the early days of cinema has survived because it was made with such fragile material, so we’re very fortunate to have this copy. At Nestlé Confectionery, we’re very passionate about our heritage and want to share that with our employees and with local people.”

Nestlé said that, according to the British Film Institute (BFI), the advert was the first talking, moving-picture advert ever made. It is kept in a specialist blast room by the BFI as nitrate film is so dangerous people need a licence to store it or project it.

A Nestlé spokeswoman said it was hoped that restoration on the footage would begin soon.

The firm hopes the Yorkshire Film Archive will also make a digital copy of the film, which can be made available to the public later.