Sheila would be the first to admit she has not achieved the box-office pulling-power of a Streisand, and she would say it without rancour. She talks freely of 'what might have been' in her career but with no sense of the unfairness of life.

Indeed she jokes about it in the offbeat, wacky, instantly recognisable way that endeared her to millions in The Frost Report and other television series.

'I have been "discovered" a lot but it goes nowhere,' she says.
' I should have gone to Los Angeles when I had the chance. I did a series called How's Your Father with Michael Robbins, playing Ivy Watkins who was always saying "Yes, Mr Cropper". They even did that on Who Do You Do?

'America wanted to take the script and me to LA and I said no.
'Why did I say no? Firstly because I had a dog. Secondly because I had a lover who was treating me so badly that I stayed, because I'm like that. And thirdly I assumed it would happen again.

'If I had gone to America, where they really like funny women, I would have been a big star by now.'

The words are spoken with no air of grandeur, no obvious regret. Sheila seems just down-to-earth, matter-of-fact.

But she does not disguise her delight at being cast as heroine Fanny Brice's mother in Funny Girl at the Minerva Theatre, Chichester.

'Fanny and her mother are absolutely two of a kind,' she points out.
'Everybody associates the show with Streisand but they adapted it to make it the Barbra Streisand story and in fact it's rather dark.

'At rehearsals the entire cast is in tears a lot of the time - not because it's so awful but because it's so moving!

'Samantha Spiro is so good as Fanny that I have to look around the room and think of something else or the eye make-up will go again.
'We are treating it more as a private piece of storytelling as opposed to a vehicle for somebody.'

Sheila first made major waves in TV's ground-breaking Frost Report in the 1960s, and she enjoyed being in the two-hour reunion last year.
'Frostie did burble on a bit but we chatted away and chose a clip we liked, and they showed the whole episode that won the Golden Rose of Montreux 40 years ago, which is what we were celebrating.'

Sheila was born in South Africa and when she moved to Britain she considered herself a straight actress.
'I was ready to suffer for my art and used to be funny just at parties. But once you start doing comedy you get lionised by it, which is OK - if you're good at something, be grateful. And it did kick-start my career.'

She has appeared with the likes of Eric Sykes and Hattie Jacques, Kenny Everett, Peter Sallis in The Ghosts of Motley Hall, the Goodies - and on stage as Harpo Marx in A Day in Hollywood, a Night in the Ukraine.

How on earth did a woman come to play Harpo?
'It's a musical by Dick Vosburgh, who died last year and who I knew from The Frost Report. He was mad about the Marx Brothers.
'I loved them too and Harpo was my favourite. I watched him a lot because when he was playing the harp he was a completely different personality.

'Dick said to me: "I've written this musical and you would be a wonderful Harpo."
I said "Great" but thought it would never happen because even if anybody could play Harpo, a woman couldn't. But a couple of months later he said "It's settled, we're going to do it".

'I used to clear my throat before I went on and then didn't speak.'
Sheila then embarks on a bewildering monologue about how she approached the role.

'I decided I should play the back wheel of a bicycle. The trick is to turn it upside down so you can play the wheel.

'Then I decided the bike wasn't well. How do you know it wasn't well? It won't eat. How do you know it won't eat? You offer it a carrot and it won't eat the carrot.

'I had some lessons in how to do the fingering on a harp. I put together a little tape of harp music and learnt the fingering for that.

'It did pretty well and I was nominated for an award, and then they decided to take it to Broadway - well, just off-Broadway actually.
'They wouldn't allow us actors in to do it but it did pretty well there and someone came back and said "Do you know, whoever played Harpo did exactly the same fingering as you did" - and she won a Tony award for my performance!
'That's life for you, babe.'

Again, no bitterness. From 1958-64, Sheila was married to Harry H Corbett of Steptoe and Son fame, and when a programme was made about him and co-star Wilfrid Brambell, she was in it.

'They put our private life up on the screen, and that kick-started me into writing it down the way it was,' she says.

'So I have just finished my autobiography after a really slow time of not working, sliding down the slid (sic), just doing the odd telly.

'I got to the end with all this downbeat stuff about my career, but then I got the job at Chichester and I thought I had to end the autobiography differently.

'So now the final line is "And then the telephone rang..."
'It really is thrilling to be doing Funny Girl.'

Sadly she has yet to find a publisher for the book, although she receives encouraging comments about it being well-written and intelligent.
'They don't think they can sell enough copies. What they mean is that I'm not a big enough name.'

*Funny Girl runs from today (April 28) until June 14.