Backstage at the Liverpool Empire, singer Barbara Dickson was in her dressing room and on her knees. Struck down by a vicious influenza bug, she had never felt worse in her life. She had been suffering for the last week but each night she had gone on stage to perform the demanding role of Mrs Johnstone in the Willy Russell musical Blood Brothers.

Now she was insisting on going on again. "Somebody came in, saw me and told me I better go home or I would die," Barbara recalls. "I had to be told to get the hell out of there."

It was the Christmas season and she was spending it away from her Lincolnshire home in what she considers her second home of Liverpool. Her three children had come to join her in the house she had rented. The  itoldest boy had arrived with the 'flu, given to the middle one who had given it to Archie the youngest.

"And Archie gave it to me," says Barbara, 57. "I had been doing the show and nursing them and they were all terribly ill. Then I caught the virus but still kept going for a week."

A reluctant Barbara returned home where she took to her bed. It had come as a complete shock to her. "I am usually in the rudest of health. But this time I was very ill and didn't get better for about six weeks. I was so upset about missing those shows."

Now she is heading back to Liverpool for a rare two-week run of the musical at the same theatre. It will be her only appearance in the touring production and at the specific request of producer/director Bill Kenwright. But the show - and Liverpool - has always been very special to her. This year it celebrates its 21st anniversary and Barbara was right there at the start when it first went on stage at the Liverpool Playhouse in 1983. "I think I must be the world's expert on Blood Brothers," she laughs.

Back in 1983 she was best known as a highly successful pop singer, a role she had taken on after her appearance in the 1974 production of another Russell show, John, Paul, George, Ringo...and Bert at the Liverpool Everyman. An awful lot happened after 1983 but the real change came after 1974. I had gone from being a very modest folk singer with a very serious outlook on everything to something very different. It was such a chasm that I had to jump over and I don't even remember jumping it. It was such an extraordinary thing.

"I tell you, I changed more in those years than any other time in my life. It was a change for the better, I suppose, but I made a rod for my own back. If I wanted to sing serious songs it was a lot more difficult to be taken seriously because of that success. People didn't taken me as seriously as they would have done without it."

She prefers to consider herself a chanteuse these days. "I don't subscribe to that middle-aged pop singer thing. But if people know you for one thing they think that's all you can do."

In its way, Blood Brothers was to change that. It was her first dramatic acting role and this time people did take her seriously. "I had never acted at all until then, I used to do music at school but no drama. So I was concerned at the time about my ability to do it. It's a famous quote of mine but I always say that if I was going to fall flat on my face I would rather do it in Liverpool than anywhere else in the country because I knew everybody would pick me up again."

Although born in Dunfermline, Scotland, her mother was a Liverpudlian and she would spend school holidays in the city. "My auntie lived in Carrington Street in Liverpool 8 and it was the sort of street where the Johnstones in Blood Brothers would have lived. It was a melting pot of people, all colours, all creeds and I would play in the street bursting tar bubbles with all the kids."

It was a change from her Scottish market town but gave her a sense of the character of Mrs Johnstone, the working class mother who is forced by poverty to give away one of her twins to the posh woman for whom she works as a char.

The Playhouse production directed by Chris Bond was a triumph. "I read the reviews the next morning and I though, oh my. They said I gave a considerable acting performances that I was convincing, all the things I hoped they might say."

Barbara went on to repeat her success in the West End and 10 years later recreated the role in t he revived Bill Kenwright production in London. So that 2001 return appearance at the Empire really was special. After the first Blood Brothers success she had appeared in television drama, worked the theatre and cabaret circuit, sung in other musicals and appeared in television specials. She had also married and brought up three children Colm, 17, Gabriel, 15, and Archie, 13. Two are at boarding school, the youngest at weekly boarding school and soon to go to full-time boarding. "He doesn't want to come home at weekends and has become very independent. So I've lost them now, they've all gone," she declares with a smile.

The touring continues - she last appeared in Liverpool at the Philharmonic Hall singing for the Woodlands hospice (she is a great supporter of hospices) - and recently completed another lengthy British tour.

Last year, she was also made a companion of the Liverpool Institute for the Performing Arts. "That was great and I met Paul McCartney for the first time. He was lovely, very nice indeed." So impressed was she with LIPA that she has agreed to go back to lecture the students. "I don't feel I am an expert on anything but I am an expert on my own experiences in showbusiness," she says.

Coming back to Blood Brothers is also an experience she savours. "The acting was important to me in that original production as Willy was one of my oldest friends. It wasn't like doing work for someone you didn't know and I really wanted it to be good."

In the show she had to play both a young and older Mrs Johnstone. "Now I am the older Mrs Johnstone acting the younger. But it is still valid when I sing lines like, 'Once I had a husband...'"

She will be rehearsing although the dialogue and songs remain in her memory. And she wants the new cast to get used to her interpretation. "I take it at a faster lick than most people and some actors get a bit of a shock when I do this incredibly energetic stuff. I come out of a door and almost knock their blocks off!"

''Daily Post', April 20014. Interview by Philip Key.