Alan Lake was sacked on the first day of filming, after getting drunk at lunchtime. He was only reinstated after his wife, actress Diana Dors, undertook to keep him sober during the film's shoot.
Dave Hill confessed to only reading the parts of the script involving his character Barry; consequently a good deal of the film came as a surprise to him at the premiere.
"The Tower of Power" Radio City was a genuine pirate station. Sited on the former Thames Estuary Maunsell army fort Shivering Sands (one of three WWII anti-aircraft defense installations built in 1943) ten miles out to sea from Whitstable, it broadcast between 1964 and 1967, transmitting on 299 metres (approx 1000 khz). By the time the film was shot, the transmitting antenna had been removed. Footage of a genuine boarding attempt on 20th June 1966 can be seen on a TV news report.