When I announce myself to Jean Marsh as being from the Croydon Guardian she immediately says with delight: "How lovely! I was in Croydon filming the Most Mysterious Murders. It was on the television just a few weeks ago. It was really spooky as we actually did some of the filming in the houses that were there at the time of the murders in Birdhurst Rise. Two of the famous Croydon poisonings took place there.

"Do you know about them? What a horrible case, we were arguing on the set as we all had a different idea as to who had done it."

Edmund Duff, who lived in South Park Hill Road and Violet and Vera Sidney, who lived in neighbouring Birdhurst Rise, all died within a year of each other from arsenic poisoning in 1928/29 and the murders are unresolved.

Jean Marsh famous for her role as the maid Rose in Upstairs, Downstairs played Violet Sidney in the case examined in the programme by Julian Fellowes. The television episode gave Jean a chance to work with Stella Gonet who played Grace Duff, Edmund's wife, who has long been regarded as the prime suspect.

"It was a real treat to work with Stella. She played Beatrice Eliott in The House of Eliott which I co-wrote with Eileen Atkins," says Jean.

As well as being an accomplished and respected actress, Jean has written articles for the New York Times and Washington Post, reviewed books for The Sunday Times had three novels published and co-created Upstairs, Downstairs again in harness with Atkins.

Born in London in 1934, she became interested in show business while taking dance and mime classes as therapy for a childhood illness.

After attending a charm school and working as a model she started acting in repertory and took voice lessons. Her rep work was supplemented by a number of film appearances as a dancer.

Three years in America followed and there she honed her craft by appearing in Sir John Geilgud's Broadway production of Much Ado About Nothing and numerous television shows.

Jean Marsh is one of those people who has Dr Who trivia links that fascinate fans of the series.

She was married to Jon Pertwee (the third Time Lord) from 1955 to 1960. As an actor she appeared in Dr Who twice in 1965 and once more as Morgaine in 1989's story Battlefield.

"I never appeared in the series while I was married to Dr Who, it's a funny business. It has changed but the core of the acting process of experience is the same.

"In my early days everyone just assumed that we'd go into rep and the rep company would get better but now that doesn't seem to happen. Young people are trained to be on camera and to use themselves not disguise themselves for character creation.

"You can't spend your life waiting for the phone to ring. The older you get you must adjust and realise you can play the old lady at the bus stop!" she laughs. "Actresses of my age Sheila Hancock and Dame Judi Dench prove that work is still out there for you."

Her latest role brings her back to the stage with the English Touring Theatre in a short tour, before going to the West End, of Alan Bennett's The Old Country. Her co-stars are Timothy West and Simon Williams. Williams has another link with Jean Marsh as he appeared in Upstairs, Downstairs as Captain James Bellamy.

Jean tells me more about The Old Country.

"I play Bron, the long-suffering wife of Hilary (Timothy West) who is a British spy in exile. He's a fantasist, very witty and funny. Things happen that make him look at his life and sentiments after 30 years of marriage."

When Hilary's sister and newly knighted brother-in-law (Simon Williams) come to visit, the British way of life is re-examined through Bennett's brilliant observations.

"The play has irony and a lot of tenderness in it. The script made me gasp at times," says Jean.

- The Old Country Yvonne Arnaud Theatre, Guildford Saturday, February 11 01483 440000