ITV sitcom Tom, Dick and Harriet, which launched in 1982, featured an all star cast but a daring stunt, in what would turn out to be the final ever episode, almost killed one of their iconic stars.

The show featured national treasure Lionel Jeffries, who at that stage of his career was beloved for roles in films such as Chitty Chitty Bang Bang and his work on the classic movie The Railway Children, as Thomas Maddison. The Saint star Ian Ogilvy played his son Richard, and Likely Lads legend Brigit Forsyth played Ian's wife Harriet.

The premise was that Thomas had come to live with his son and daughter-in-law following the death of his wife. Only twelve episodes were ever made, but the final episode features a stunt that almost became a huge tragedy. Star Ian Ogilvy recalled the incident in Channel 5's When Comedy Goes Horribly Wrong.

He explained: "A lot of the comedy was me trying to be a piggy in the middle and be nice to both sides. In one episode, Dick bought an old banger with the thought that it'll get his father out of the house. The concept was that I should teach my awful old father how to finally, how to drive."

The finale of season two was to be a stunt filmed by the side of a lake, with the idea being that Tom would drive up to the edge of the lake and into the mud. He and Richard would step out, squelch their way through and get back home again, soaked and wet. According to Ian, the actors were told the water in the lake had been measured and was only 2 feet 6 inches.

With the camera rolling and Ian recalled: "The scene starts, and we drove into the lake. The car goes in... we did a little bit of acting, and the water started to come a little bit. And I said, Lionel I'll get out now. And he went,' OK, I'm bit worried about this'. I said: 'Don't worry. It's only 2 feet, 6 inches deep."

However, the water turned out to be much deeper than that, and as Ian sits on the roof of the car, Lionel remains trapped and in outtakes can be heard screaming: "Quickly, I can't get out!" as he pleads for help.

In a comedy of errors the motorised dinghy which was on hand in case of an emergency wouldn't start and the car continued to sink as Lionel fianlly managed to make his way out of the car before it ws sucked to the bottom of the lake - which transpired to be closer to 45 feet deep.

"It's a fairly near-death experience," Ian told the documentary. "You see what that car does quickly, it disappears under the water. I was told later on that it took them about a day with divers to find the car, and it was in 45 feet of water."

While it is widely acknowledged modern health and safety standards wold never allow such a stunt nowadays it appears it was also too much for the standards of the time as it was the death knell for the sitcom which was regualarly watched by well over 10 million viewers - figures contemporary shows could only dream of.

"Lionel Jefferies was in a state of profound shock, and was in hospital for the next week, just lying there crying, which is one of the reasons why the series didn't really go on much after that, because he just lost all faith, really in it, and had such a horrible experience that he said, 'That's it'.

"But it was a pity, because it was very popular," Ian refected.