In its opening scene the programme promises “seat-gripping action”, “knee-gritting suspense”, “spine-raising horror” and “gallstone-jangling drama” and later there are sketches with a silly walking doctor, a patient with too thin legs and a wrestler who throws himself around the ring.

There is also a man walking into a shop looking to buy some chartered accountants and another episode that spoofs TV news broadcasts including a vox pop on the increasing problem of publicity-seeking vicars.

If it all sounds a bit Monty Python or The Goodies, there’s a good reason. The show is At Last the 1948 Show, which starred John Cleese, Graham Chapman, Marty Feldman and Tim Brooke-Taylor and the BFI will on Thursday announce it has rediscovered two “lost” episodes.

The almost complete episodes were discovered in the archive of the late David Frost, who was the show’s executive producer. Dick Fiddy, who heads the BFI’s Missing Believed Wiped project to rediscover lost programmes, said he was thrilled on a professional and personal level. “I was a big fan of the show at the time, I’m that sort of age, and I had the LP of it – so I remember a lot of the sketches. To now see the visuals put back on sketches I’ve known so well is a fantastic thing, a real treat.”

Facebook Twitter Pinterest John Cleese, Tim Brooke-Taylor, Graham Chapman and Marty Feldman. BFI/Archbuild/Associated Rediffusion

All four men worked on the somewhat regimented The Frost Report and Frost wanted to free them of their shackles, said Fiddy. Unlike a lot of comedy from the 1960s, the episodes hold up remarkably well. “The reason it seems less dated than other stuff,” said Fiddy, “is that you are seeing people who were off the leash. They freed them up to be a bit more surreal, a bit more experimental and to start exploring those areas that would become The Goodies and Monty Python.”

It was called At Last the 1948 Show as a joke on how long it took TV commissioners to actually make a decision and featured sketches poking fun at other programmes on TV at the time. They also feature “the lovely” Aimi MacDonald as a glamorous continuity announcer who assumes that the show is all about her. At one stage she even says “and now for something completely different”.

Facebook Twitter Pinterest John Cleese in the ‘gallstone-jangling drama’, a precursor to The Goodies and Monty Python. BFI/Archbuild/Associated Rediffusion

The new episodes are particularly important because they are the first ever shown and the last one of the second, final series. The shows have been near the top of the wanted list for some time and it was only 25 years ago that only two were known to still exist. Since then, compilations have been found in Sweden, while other episodes have been found in Australia. There was even one fan who diligently audio-recorded each episode from his television.

The shows were important stepping stones for all four performers, with Feldman in particular becoming an instant star and offered his own colour BBC2 series. Feldman, who survived on black coffee and 100 cigarettes a day, died aged 48 from a heart attack in 1982. Seven years later, Chapman died, aged 48.

Facebook Twitter Pinterest The credits of At Last the 1948 Show. BFI/Archbuild/Associated Rediffusion

Brooke-Taylor has already been to the BFI to see the lost episodes and Cleese will be a guest on 7 December where he will discuss the series on stage. The discovery of the programmes is part of the wider project to rediscover lost programmes wiped from existence at a time when anyone suggesting that TV programmes should be repeated would have been laughed off the premises.

Fiddy said the hunt for At Last the 1948 Show had been particularly successful with more or less nine of the 13 in the bag. “The recovery of this show has been extraordinary, spectacular.”

Included on his wishlist is Alan Bennett’s 1966 satirical BBC2 series On the Margin (though the audio has been recovered), while Fiddy’s “holy grail” is the 1963 Sunday night TV play Madhouse on Castle Street, which featured a young folk singer called Bob Dylan.

“If that turned up, it would just make you think anything is out there,” said Fiddy. “People have been diligently looking for it for 50 years.”