Imelda Staunton has always made choices that steal the limelight

In 2011, as Imelda Staunton rehearsed for a revival of Stephen Sondheim's Sweeney Todd at the Chichester Theatre, she received a visitor backstage. It was Sondheim himself, come to say he was so impressed by her performance as Mrs Lovett, the baker of human-flesh pies, that he wanted her to play Mama Rose in his Gypsy. When it comes to receiving a divine imprimatur in showbiz, there's no higher accolade.

Playing the ultimate stage mother, derangedly pushing her daughters on the vaudeville circuit, the fiery Staunton won the 2015 Evening Standard Theatre Award for Best Musical Performance. She has brought the house down in musicals before – as Dorothy in The Wizard of Oz, in Sondheim's Into the Woods, as Miss Adelaide in Guys and Dolls at the National in the 1980s – so it's startling that she's on record saying she doesn't much care for them. Nor does she like Sondheim's music that much. That's Ms Staunton for you. Though she may do a brilliant impersonation of Ethel Merman, she doesn't buy the whole Broadway-baby shtick. She likes good stories and good tunes – and the audience's reaction.

Her parents were London-Irish, her father a builder, her mother a dominant, fiddle-playing hairdresser. An only child, Imelda grew up loving Sinatra and Dean Martin movies. At convent school in Archway, her elocution teacher spotted her talent and steered her towards Rada; by 26 she was at the National.

Her career is filled with non-showbiz, meaty, challenging, parts, involving driven and single-minded women, from the backstreet abortionist in Vera Drake to the show-stealing Dolores Umbridge in two Harry Potter films. This 5ft 2in tall powerhouse has always made choices that steal the limelight, that put her in charge, like her adored mother running the London salon. "All of it," she says, "comes from the Celtic thing."