The 78-year-old played Barbara Good alongside Richard Briers as her husband Tom.
She revealed Richard, who died in 2013, helped recruit her to the show after being impressed by her appearance in the West End.
And while the pay was not up to much, she has nothing but fond memories of the show, about a suburban couple who quit the rat race to live off the land in Surbiton, south-west London.
Felicity said: "Dicky Briers was one of the great human beings that was also an actor.
image [https://cdn.magzter.com/1583517504/1742265282/articles/OEnjTVQ4lFiItBbH83sys/2612672142.jpg]
He said, 'I'm going to do this little television series, may I send you the script for the part of the wife? It may not do well because it's a very unusual subject."
They all had great chemistry from the off. Felicity recalled: "We invested in it because we liked it, rather than we thought, 'This is a snazzy job'.
"It wasn't at all - the BBC didn't pay very well then.
"But it just worked and it was a very special job for all of us."
The gentle comedy, which also starred Penelope Keith and Paul Eddington as neighbours Margo and Jerry, began on April 4, 1975, and ran for four series.
A Christmas special in 1977 drew 21million viewers.
It ended in 1978 with a Royal Command Performance recorded in front of the Queen. Half a century on, Felicity remains "terribly proud" of what they achieved, thanks to the scripts by John Esmonde and Bob Larbey.
"The way it was written is the major thing; without the writing, you've got nothing to play with," she told Radio...