Lisbon 1492: Christopher Columbus sets sail with his brother Bart and a motley crew, made up mostly of refugees from the Spanish Inquisition, to discover a direct sea route to the Far East. He does not realise that two spies, planted by the Sultan of Turkey, are on board.
With many of the original Carry On regulars (Sid James, Hattie Jacques, Charles Hawtrey, Kenneth Williams, Kenneth Connor) no longer with us or (sensibly) otherwise engaged, it was left to more contemporary comedians such as Alexei Sayle, Julian Clary, Rik Mayall and Tony Slattery to put the final nail in the Carry On coffin with a cacophony of puerile jokes and plenty of general atrociousness.
This mainly fails because the Carry On films are part of British comedy nostalgia, and, like many other historic things (the three-day week, the Blitz), they are probably best remembered rather than re-created.
Perhaps the other reason this flopped is because the supposedly serious Christopher Columbus: the Discovery, with Marlon Brando, Catherine Zeta Jones and Tom Selleck, released in the same year, was much funnier.
Duke of Costa Brava