Andy Richardson: Class act Jim adds a new string to his bow

His grandchild was looking forward to a significant birthday so Jim was buying food and drink for 80. Lucky kid. Celebrating your 18th with the world's coolest granddad is the only way to party. I hope he serenaded her with Coz I Luv You.

But when Jim did call, the usually out-of-circulation bass-playing, Slade songwriter could have talked for hours. And he very nearly did. We ran out of time initially – Steve Punt, one half of Punt and Dennis, was due on the other line and we had to call it a day. So Jim called back a little later to make sure we'd got all we needed. You can't buy class. And he had it in spades.

Jim's a fascinating man. Typecast as the curly-haired quiet one with one of the greatest pop-rock bands of them all, he's always been viewed as the man who doesn't say much; a dyed-in-the-wool technophobe who happily admits to not using email or a mobile phone.

While the other members of Slade were partying and trying on new be-mirrored top hats or stack heels, he was probably sitting in the corner gazing at the sky.

Never a naturally-public figure, Jim was always the guy standing to the side. While Noddy Holder relished the applause and Dave 'Platform Boots' Hill was next in line, Jim was there but never there.

A man who lived in his own head, rather than in the full glare of the spotlight, he retreated into the shadows where it was safe to write 17 consecutive top 20 hits, six number ones and mastermind the band's status as the most successful British group of the 1970s.

Every Lennon needs a McCartney, every Liam needs a Noel and Slade probably wouldn't have made it out of Walsall without the songwriting brilliance of Lea. He was the one who added substance to their style, who meant they could walk the walk as well as talking the talking. Jim was the engine room and the fulcrum, the glue that bound.

There's an art in not outstaying your welcome. And Noddy knew when to call it a day on the band. After 25 years, a successful comeback and belated American breakthrough followed by a second decline in popularity – hell, at that point, they couldn't get arrested and even their Greatest Hits album stalled at number 89 – Noddy did the sensible thing and left. Jim explored the options of bringing in another frontman, but realised no one could cut it like Nod, so followed him into the world of retirement. Dave and Don Powell teamed up with three other musos to flog a dead horse in Slade II, which was never going to be a good idea.

Marilyn Monroe was right about break-ups: "Sometimes good things fall apart so better things can fall together."

And, in Jim's case, that's what happened.

The man who had lived in his head while the Slade brethren were partying their way around the world decided to study what had been going on in his mind for all of those years.

The man who co-wrote Skweeze Me Please Me, Mama Weer All Crazee Now and who wrote My Oh My after listening to Noddy and Dave tuning up before a gig at the University of Wales and imagined 'bagpipes' decided to study psychotherapy.

He decided against taking it up as a career; mindful, perhaps, that potential patients might run a mile when lying on the couch beside a man who used to earn a crust by dressing in tartan and knee-length boots. "And you think you've got problems?"

The kid who grew up in Bilbrook and was inspired by jazz violinist Stephane Grappelli rather than Little Richard or Elvis learned other stuff.

He immersed himself in particulate psychics and became probably the only man to have written six UK number one hits and develop a working knowledge of string theory.

String theory, for the uninitiated, describes the the way in which strings propagate through space and interact with each other.

It's the sort of thing that you normally hear around the dinner table at King's College, Cambridge, as masters pass the port – rather than in the dressing room of Bilston's Robin 2. But then Jim's always been a one-off.

His next record will feature violins, cellos, double bass and other instrumental music.

And, you guessed it, he's calling it String Theory.

"I don't blow and I don't hit," he says.

And he's referring to musical instruments rather than recreational drugs or hand-to-hand combat, before you say it.

Jim started his career in the year when England won the World Cup. And he's still as creative as ever.

Cum On Feel The Noize. God love him.