The rolls of celluloid may not be thousands of years old, but for fans of Peter Sellers the discovery of two films long believed lost has been hailed as the film equivalent of “finding the Dead Sea Scrolls”.

Dearth of a Salesman and Insomnia Is Good for You, which were both made in 1957, before Sellers had become a global film star, have not been seen for 50 years, and it was assumed that all versions had been destroyed.

But today it emerged that copies of the films, which run to around 30 minutes each, had been found in a London skip and will be digitally restored to open the Southend Film Festival in May next year.

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Very little was known about either work in recent years, and the head of the film festival said it was “busy researching and trying to speak to people who might have been involved in their creation”.

Building manager Robert Farrow stumbled upon the reels while clearing out the offices of Park Lane Films, the now-defunct production company that made the movies.

Mr Farrow oversaw the refurbishment of the block in 1996 and spotted 21 film cans in a skip outside the block and “thought they would be good for storing my Super 8 collection in. I took them home, put them in a cupboard and pretty much forgot about them.”

In a recent clear-out, he investigated the contents to discover they included the negatives, titles, out-takes and master prints of the two films.

“It was amazing,” Mr Farrow said. “I knew I had something, but it wasn’t until I called Paul Cotgrove, who organises the Southend Film Festival, that it dawned on me that I’d found something very special indeed.”

After researching the films, Mr Cotgrove said he was “gobsmacked” to realise film historians considered the two films lost. “Robert’s find is the Dead Sea Scrolls of the film world,” he added.

The actor Neil Pearson, who collects rare books, owns the only known script of Insomnia Is Good for You. “No biographer of Sellers that I’ve spoken to has managed to find the film,” he said recently.

The films will interest fans as they were recorded right at the beginning of Sellers’s screen career, after he had risen to fame as part of The Goon Show on the radio.

Mr Cotgrove said Sellers “almost appears to treat them as show reels to demonstrate to film producers his considerable talent”.

They were co-written by the Canadian screenwriter, author and essayist Mordechai Richler, and Dearth of a Salesman is believed to feature Judith Wyler, the daughter of the Oscar-winning director William Wyler.

Dearth of a Salesman saw Sellers play Hector Dimwittie, who attempts to become the most successful salesman in Britain, vainly trying to sell goods from toilet supplies to tape recorders. “Sellers works hard,” Today’s Cinema said at the time, before adding that there was “handy footage appeal”.

His character, Hector, also featured in Insomnia Is Good for You, now unable to sleep over a forthcoming meeting with his boss. Monthly Film Bulletin said it “falls very flat”.

Dimitris Verionis, from the Peter Sellers Appreciation Society, said he “cannot wait” to see the restored films. “Their screening celebrates the wonderful comic talents of Peter Sellers.”

Sellers, who died in 1980, made a string of hit comedies and became synonymous with the character Chief Inspector Jacques Clouseau in the Pink Panther films.

His film career began to take off the same year the two lost films were made, when he starred opposite Terry-Thomas and Peggy Mount in The Naked Truth.

Other notable roles included in Dr Strangelove, What’s New Pussycat? and The Party, and Turner Classic Movies called him “one of the most accomplished comic actors of the late 20th century”.