I’m a bit sceptical about big names being parachuted into West End productions. But when I saw that the critics had given ex-Spice Girl Melanie C a standing ovation on the first night of her spell in Blood Brothers I couldn’t resist booking tickets. Critics are a steely bunch so if Melanie C’s debut acting performance managed to get them all on their feet the show had to be worth seeing.

And it is. Aside from her sporty tracksuits, jaunty pony-tail and back flips, Melanie C was best known during her Spice Girl years for being the only one who could actually sing. Well, she can act too. She grew up on Merseyside and is utterly compelling as Mrs Johnstone, the Liverpudlian mum who, on her uppers after her husband walks out leaving her with seven children and two more on the way, agrees to give one of her twin sons away to her snooty employer. She desperately hopes that she’s offering him the chance of a better life but the two brothers, neither of them aware of each other’s existence, aren’t so easily parted.

I’ve been to Willy Russell’s wonderful play several times during its 21-year history but Melanie C knocks spots off the other actresses I’ve seen in the part. Her voice is stunning and she’s got exactly the right blend of toughness and vulnerability to make Mrs Johnstone believable. Even more impressively, she’s insisted on doing all eight performances of the show every week. “I don’t think I have ever had a prima-donna reputation and I don’t intend to start now,” she says.  “I’m new to this and I have to pay my dues.”

Even so, the new mum must be drained when she leaves London’s Phoenix Theatre every night. This emotional roller-coaster of a show is exhausting enough for the audience (on the night I went everyone left with tear-stained faces) so goodness knows what it’s like to star in it.

PS: Watch out for Stephen Palfreman, who is simply wonderful as Micky, the bad-boy twin who stays with his mum.