She's a national institution, showbiz royalty and has been open and honest about her 'mistakes'. But there's more to Dame Barbara Windsor than turning on the charm for the cameras, which, she tells Gemma Dunn, is what she hopes new BBC biopic Babs will reveal

Ask anyone to define nation's sweetheart Dame Barbara Windsor and the response will typically flit between the pint-sized bombshell who perfectly captured the saucy slapstick comedy of the Carry On films, and iconic EastEnders' matriarch Peggy Mitchell.

There's also much known about her chequered personal life: her first marriage to gangster Ronnie Knight, her adulterous affair with Carry On co-star Sid James; her further two marriages to younger men, and her five abortions. She's never been shy about sharing her deepest and darkest secrets. But there's more to 'Bar' than bikini-popping scenes and hollering, 'Get outta my pub', which TV writer Tony Jordan intends to show in BBC One's upcoming biopic drama, Babs.

Set in Catford's Broadway Theatre, the 90-minute special follows the heart-warming story of the showbiz favourite from 1943 to 1993, prior to making her mark in EastEnders. Promising "warts 'n' all", viewers will see four actresses tackling the 50-year period, including Jaime Winstone, who'll portray Windsor during her 20s, and Samantha Spiro (who has previously played the star on stage in Cleo, Camping, Emmanuelle And Dick; plus the TV production of Cor Blimey!), who'll play Windsor in her mid-50s.

The actress herself - who also makes a cameo - believes it's the right time to put the story out there. "I used to hear it: 'You should write your life story and all the rest of it'," says Windsor, explaining that she agreed to it "when darlin' Jordan said, 'I want to write this for you', 'cause I know him and I love him."

The 79-year-old counts the screenwriter as a close friend, following his time as lead writer on EastEnders. "Believe it or not, he got me and Peggy," she says. "He won't make me something I'm not.

"I knew certain people in my life wouldn't like it - not you, Scott," she continues, glancing over to admire her husband of 17 years, Scott Mitchell. "But there's a couple of people who see me in this showbiz-type way and they'd say, 'Can we have a little bit more showbiz?' And I said, 'That's showing off; this is the real me, this is what people don't know about what made me'."

Born in Shoreditch to a "cockney" barrow boy-turned-bus conductor father and dressmaker mother ("she wanted to be this posh lady"), Windsor - real name Barbara Ann Deeks - first realised her knack for entertaining when she took up dancing after being evacuated to Blackpool during the Second World War. She landed her first job aged 13 - which she credits with giving her the humility she maintains today.

"It was with the great theatrical impresario Emile Littler and he said, 'Look, you've all chosen to come into this business, we didn't ask you, well these are the rules...' And of course he let out all these rules: know your lines, be on time, do not talk to any leads of the show until they talk to you," she details. "There were masses and that's how we were, and that's how I was brought up.

"The Carry Ons were like that too - very on time," adds Windsor, who has since gone on to work on Broadway and in the West End, as well as across TV and film. "Oh gosh, I made one slip on my first line and Kenny Williams said, 'Do get it right, ducky!' I was so nervous of this great gang, but that's how it was."

It's a mandate she extends to her fans, too. "Don't forget as you step outside, 'You've chosen to come into this business, people haven't chosen to be entertained by you, you've chosen to entertain, so don't forget when they come up and say, 'der der der', you be ready', so I am. It takes me ages to get a loaf of bread, but that's what it is!" she adds, her brilliant cackle in full force. "I love it, and the day they stop, I'll be very unhappy."

Windsor is professional and charming company, in every sense of the word. She turns up on time, is polite, warm (opening with her trademark "hello my darlin") and incredibly honest. In fact, she's a journalist's dream.

"You're the one thing that Sir Emile Littler said: 'The press. Remember the press, they can make you and break you'. That was when I was 13!" she notes. Tottering in on her stilettos, her perfectly coiffed beehive and dazzling smile in check, she finds it hard to believe she'll be celebrating her 80th birthday this August. "It's daft, isn't it?" she shrieks. "It's really daft to be 80, but I'm in a good place in my life: I've got a great husband, I'm still working and I can do all my charities.

"It's a bit difficult now I am a Dame - I have to watch how I behave!" she says, grinning at the mention of her 2016 DBE appointment. "That was a shock. God was that a shock. But life is good."

Does she have any regrets about living out her extraordinary life in the public eye? "Well, I wrote a book [her 2001 memoir All Of Me] and because I'm quite honest and I wrote things in the book which had happened to me, I got a bit of a knocking," she acknowledges. "Maybe I shouldn't have done that, maybe I should have kept it quiet. But then I'm like that, I'm your honest little cockney.

"The thing is, maybe they'll understand it a bit more - how and why those things happened," she says, referring to her story being brought to screen. "I'm a nice lady; I've made mistakes, but they're my mistakes. I'm ashamed of some of the mistakes I've made. It would be different if it was now - but at the time, that's what I did.

"I always think the decade I'm in is the best," Windsor adds. "I'm very happy and I always find good things; my life has been great."

  • Babs airs on BBC One on Sunday, May 7