WEST End and Broadway leading lady Kerry Ellis had expected to return to the role of Mimi in Rent for “only a few concerts” to mark the 20th anniversary of Jonathan Larson’s rock musical.

“But there was such a crazy demand for the show that it ended up being a two-week tour of ten or 11 shows, then there was a November leg that I didn’t do, and now we’re doing another 15 shows,” says Kerry, whose autumn absence can be explained by the arrival of her son, Alfie, now 12 weeks old.

Larson’s tale of impoverished young artists and musicians falling in love, finding their voice and living for today, against the creeping shadow of HIV and Aids in New York’s Lower East Side, takes the form of a “sung-through” musical. In other words, songs rather than dialogue drive the show, and so a concert version is pretty much indistinguishable from the full-scale musical.

“We have a set; we have costumes; we use the stage to the full. It’s not your normal concert, where you go on, sing your songs and go off,” says Kerry. “The show demanded that extra flavour, not just the songs.”

Rent’s story, with its spectre of death and lives cut short, is as resonant as ever. “The only difference is that 20 years ago it might have been more shocking – the homosexuality and lesbianism – but the issues of drug addiction and HIV are still very relevant and the show will still leave people thinking.”

Kerry plays Mimi, who is struggling with addiction. “But she’s a fun part because she’s carefree, wears her heart on her sleeve and is a little bit vulnerable,” she says.

Rent’s music is “right up her street”. “It’s rocky, it’s dramatic, it’s emotional – and I think that when someone goes out on a limb and writes a new musical, when he isn’t known as a main name on Broadway, it has to be interesting to survive, which Rent is,” she says.

Kerry’s diary has been as busy as ever with sundry commitments, among them filming a cameo role in the movie version of Les Miserables. “I took part in the pub scene, which was great fun, and it was nice to be involved as I think most of the people who had been in the West End stage show were in it, so it was nostalgic to do it together,” she says.

Kerry sang in the arena tour of Jeff Wayne’s The War Of The Worlds, playing opposite Marti Pellow, and became involved in Virginia McKenna’s Born Free campaign with Queen guitarist Brian May, who also runs the Save Me wildlife organisation. “We went out to South Africa, where we did an impromptu performance, just Brian and me,” she says.

“We ended up recording Born Free and doing a UK tour and we’re about to do another week from February 17 before we then go out to Russia. We’ll do anything we like doing, from Barbra Streisand and Cream to the Everly Bothers. A good song is a good song.”

• Kerry Ellis stars in Rent, 20th Anniversary Concert, Grand Opera House, York, February 12, 7.30pm. Box office: 0844 871 3024 or atgtickets.com/york