THE percussionist and occasional bass player of T Rex, Mickey Finn had a role in the group that went far beyond his musical contribution.

In photo shoots and on album covers his straight, raven hair and handsome, pale face became the iconic counter to Marc Bolan’s dark eyeshadow and frizzy mane. Arguably, his admission into Tyrannosaurus Rex in 1969 marked a point — both in the group and in pop music generally — when style had become more important than substance.

After playing with the bands Hapshash and Coloured Coat, Finn was taken into Tyrannosaurus Rex as a replacement for the wayward Steve “Peregrin” Took — the other half of the band — whom Bolan had all but abandoned in Los Angeles. With Finn’s arrival, the whimsical Tolkienism of Tyrannosaurus Rex petered out (Took’s ersatz middle name had been added in honour of a mischievous hobbit in The Lord of the Rings). The album Beard of Stars was the last made with the original name.

When Bolan and Finn returned as T Rex in October 1970 with Ride a White Swan, the nonsensical lyrics about pixies remained, but a brasher, edgier sound had been crafted, with Bolan’s shift from Donovan-style acoustic guitars to an electric Sunburst Les Paul and massive amplification — earning the band the No 2 spot in the charts.

Despite Took’s undoubted musical ability, Bolan was not sorry to replace him with someone of more modest talents who would cause less trouble. Took’s massive appetite for drugs and desire to inject his own, hard-rock influence on the band had not been welcomed by Bolan, who was determined that any group he was part of would be his own.

Finn fitted in perfectly — he had little inclination to progress from his role as sometime percussionist (a “proper” drummer was hired in 1973) and full-time teen idol. Bolan would later say of him: “He can’t sing a note, but he looks superb.”

Finn did bend the group’s sound to a more “be-bop” feel, best felt on Get it On and Telegram Sam, and he eventually became a fair bass guitarist. More importantly, he was extremely close to Bolan and a vital confidant during the star’s constant emotional traumas.

As the hits and money rolled in, however, Finn embarked on week-long drug, drink and sex binges in hotel suites. Eight consecutive songs — including Jeepster, Children of the Revolution and 20th-Century Boy — all went to the top end of the British charts, yet the reign of T Rex over the chart was remarkably short given their success — partly because they never cracked the American market.

By 1975 the critics, irritated by Bolan’s inability to develop his style beyond three-chord sledgehammer riffing, became increasingly vicious. Bolan began to throw tantrums, and tried to cut down the earnings taken by Finn and the other members of the group — already modest by comparison to his own cut.

Bolan declared T Rex extinct in March 1975. Thereafter he gave up all toxins, made a massive effort to recover his health and embarked on a comeback tour, making the most of the admiration he enjoyed among some of the emerging punk groups and their fans.

Finn, meanwhile, now playing guitar with the Steve Marriot Group, sank deeper into drugs and alcohol. His problems were exacerbated by Bolan’s death in a car crash in 1977. He would later say: “Marc’s death unhinged me. We were more than brothers.”

Ten years later Finn had lost his looks and all his fortune, and returned to live with his mother in Norwood, South London. In 1997 he turned up for a show in Cambridge to commemorate the 20th anniversary of Bolan’s death.

He decided to reform T Rex with Paul Fenton, who had joined T Rex as drummer in 1973. This original pair, with four other musicians, gigged extensively throughout Europe and Japan as Mickey Finn’s T Rex and in 2001 released an album of rehashed T Rex classics called Back in Business. Finn was considering moving on to new material and was due to resume touring with a string of gigs in Norway.

Finn accepted a ribbing from Sean Hughes and Mark Lamarr on BBC Two’s Never Mind the Buzzcocks last year and, despite his altered looks, was quickly identified. More auspiciously, he played to 2,000 hardcore fans, along with Bolan’s son Rolan, on the 25th anniversary of Bolan’s death last year.

During a revival of interest in T Rex’s music in 1991 — for which he received no reward — Finn accepted his poverty but expressed his frustration that his role in T Rex had been eclipsed by his closest friend.

“I was an important part of T Rex and I don’t want it forgotten,” he said. “I hope people will remember Mickey Finn as well as Marc Bolan when they hear T Rex records . . . I would be deeply hurt if I was totally forgotten.”

Mickey Finn, percussionist with T Rex, was born on June 3, 1947. He died in London on January 11, 2003, aged 55. He had been suffering from liver and kidney problems.