I reviewed Ben Elton's Rod Stewart tribute musical Tonight's The Night when it opened in London three years ago and castigated some of my fellow critics for their po-faced attitude to the show. One called it "eye-poppingly, knee-huggingly, mind-bogglingly awful", while another panned it as "formulaic garbage". "Lighten up, guys and gals!" I advised. "In slating the musical for its tackiness and vulgarity, reviewers have overlooked the fact that this feature of the production is there by design rather than accident a reflection of the persona Rod himself projects."

His principal interests in publicity terms at any rate are "Booze, Balls and Birds", as they are spelt out on the coat of arms adorning the entrance to Rod's mansion (as imagined by set designer Andrew Howe-Davies). We never see inside the gates or, of course, meet the man himself. The words raised a big laugh as the touring version of Tonight's the Night opened on Monday to a packed house at the New Theatre (where, in December 1973, I saw Rod strutting his stuff as leader singer of the Faces).

But since this is the politically correct 21st century, and the show comes with the full backing of Stewart (his manager Arnold Steifel is co-producer), he can't be allowed to appear too much of a 'rock pig', to use an expression gleefully bandied about on stage throughout the evening. "He has never hurt a woman in his life," says Tiffany Graves in the role of Rod's 'rock chick' manager Baby Jane Golden, whose word we must, of course, take on this subject.

Or must we? For this is a show of distinctly mixed messages. If Rod is so pearly white, how is it that grease monkey wimp Stuart Clutterbuck (Ryan Molloy) becomes so complete a 'rock pig' once he has taken over Stewart's soul as part of a Faustian bargain with the devil (feisty Ms Graves again)?

On the whole it is best to dismiss such questions, and sit back and savour some wonderful songs and first-class performances of them. From the opening number, a joyful company take on Young Hearts Run Free, to the stirring (if predictable) finale of a flag-waving Sailing, this is a feast of memorable music, skilfully interpreted by an on-stage band under Griff Johnson. Nor are they simply slavish imitations of the originals: there is a hint of a country flavour, for instance, in You're In My Heart, which is developed into a full-scale hoedown, complete with fiery violin in You Wear It Well.

To Mr Molloy looking a tad absurd in over-long pointy boots falls the main task of 'doing a Rod', which on the whole he handles with skill, not least in such signature numbers as Maggie May, Hot Legs and Stay With Me. There is fine singing, too, from Rachel Tucker, as Stuart's loyal long-term love Sweet Lady Mary, and Daniel Robinson as the good-sort Rocky, who gives a show-stopping account of I Don't Want to Talk About It.

Welcome comedy is supplied by Jeff Edwards, as Stuart's drawling, permanently stoned tutor in the louche lifestyle of the rock star. His 'Stoner' is a compendium of most members of the Rolling Stones, but especially 'Keef'.

Just one question: at the end of the show in London designer Lez Brotherston's Gasoline Alley garage set transformed memorably into a ship going full steam ahead during the Sailing close to the show. With Andrew Howe-Davies's design, though I could see obvious lifebelts behind the petrol pumps, the same did not happen. Is this an economy measure for the tour, or did some mechanism malfunction?

Tonight's the Night, directed by C.Jay Ranger, continues until tomorrow. Box office: 0870 606 3500.