Several years before I started the programme, my right knee became very arthritic.
In 1980, Sheila's problem became Annie's problem.
Bending to pick up an orphaned lamb in the farmhouse kitchen in the spring of 1980, Annie was gripped by a sudden pain in her knee which caused her to cry out.
Dolly immediately came to her aid, but Annie brushed off her concern: it was just a passing thing: "Bones get old," she said.
But a few weeks later the pain struck Annie again as she bent to pick up a dropped item of shopping. And if she was entirely honest with herself she had to admit that wasn't the only time.
Dolly agreed not to tell the menfolk, if Annie would agree to go to the doctor. This she did, and her knee was x-rayed. Meanwhile, Dolly couldn't help communicating her concern to Matt, who told Jack.
By the end of the year, the pain was worse than ever and becoming more frequent. In 1981, Annie's knee was operated on. In a great piece of soap realism, Sheila Mercier's absence from the show was for exactly the same reason.
In 1988, TV critic Hilary Kingsley wrote that Sheila Mercier had made a "small chapter of soap history":
She underwent surgery for an arthritic knee on and off screen. Until then ailing actors and actresses simply disappeared for operations, and no one mentioned their absence.