Stranglers 21st anniversary concert Royal Albert Hall, London

If the 18-piece all-girl electric chamber orchestra Electra Strings are anything to go by, the Guildhall School of Music doesn't just require grade eight violin but long legs, a full chest and peachy looks. In their stretchy white tops and camouflage trousers, they looked terrific. (If that sounds a gender-specific, it has to be said that Stranglers' concerts are laddish affairs - at this one the band's set was preceded by a dire exercise in "gut-barging".)

As for how the Electra Strings sounded, I'm not sure. Plugged into the Stranglers' sound system, the strings became aural soup. Over-amplification did for audibility. Their cellist I could see bowing passionately away, but what she added to "Always the Sun" and "All Day and All of the Night" I couldn't tell.

What was clear was they were overused. To run a string orchestra behind a band that once snarlingly claimed to be essence of punk is a novel idea, at least for a few numbers. But to have Jocelyn Pook and her 17 colleagues climbing the wall of sound behind every one of what was basically a greatest hits compilation concert made everything sound a bit samey.

Homogenisation is an odd fate for a band that has reinvented itself drastically. The Stranglers were once synonymous with punk ("No More Heroes" is still one of the great late Seventies get-'em-on-their-feet anthems). By the early Eighties, they were producing lustrous mainstream pop - such as "Golden Brown". With the departure of lead singer Hugh Cornwell seven years ago, a vital spark went out. The Stranglers are a professional even slick show band; what they do these days is showbiz.

On parade at the anniversary concert was the latest line-up. Paul Roberts as lead vocalist does a pretty fair imitation of the original, down to stripping off his shirt and having his shoes and socks removed by the front row in approved Seventies fashion. JJ Burnell on bass now has John Ellis alongside on guitars with old stagers Dave Greenfield and Jet Black on keyboards and drums respectively. They all perform with verve, though it's hard to escape the sense that routine took them over long ago.

Perhaps long-lasting groups survive because at a particular moment enough fans form an allegiance that sticks, which then carries them on through thick and thin. To judge by the Albert Hall audience, the Stranglers' moment came later than when they were doing "Peaches" (another punk classic). Among the fans I counted only a couple of full mohicans - most of the audience looked pretty ordinary, which may mean ex-punks do indeed cut their hair and become accountants. I am looking forward to listening to the CD of the event, if only to be able to hear what it was the prettycellist was actually contributing to the anniversary party.