He's a little bit of a miracle as an actor. He can play a polished barrister with ease - James Kavanagh QC - or a thoughtful, opera-addicted detective - Inspector Morse. Not bad going for a lorry driver's son from the wrong end of town with one O-level.
Not bad for a lad who wanted to be a stand-up comedian.
Yes, it's true. You can see Jack Regan of The Sweeney perhaps getting up there, but not Thaw. As a teenager back on his home terrain in Manchester the emerging John Thaw was an arrogant, brash young chappie. Not the inhibited, shy product we see before us today, sporting a mop of pure white hair flopping down over his collar and a rather smart beard.
Even he can't quite believe what he got up to in the working men's clubs and old people's homes when he was bidding to emulate Max Miller, Jimmy Wheeler and Arthur English. He idolised the Cockney comedy breed.
"They were jokes I had nicked off the radio," he explains with a degree of embarrassment, shifting on a sofa. "I did fancy myself as a comic. At that stage I was quite an extrovert, believe it or not, so I quite enjoyed the act of standing up and showing off. I got a thrill out of that.
"I liked the cheeky chappies. I'd hear them on Sundays and think `I'll have some of that'. I think I was very much in love with the idea of making people laugh. But at school there were people who thought I might just have what it takes as an actor."
After leaving Ducie Technical High School in Manchester he became an apprentice baker's boy. Friends told him he was potty but he reckoned he should give acting a stab.
And so it was that Thaw, and this is little known today, at the age of 16 became one of the youngest pupils in the history of the Royal Academy of Dramatic Art. He read a piece from Othello and a French classic at his audition.
They were so impressed they told him to keep his age a secret. You had to be 18 to gain admission and a grant. His old headmaster pleaded his case to the local authority. They were impressed enough to hand over the funding.
"The principal of RADA said, `Come along, but if anyone asks tell them you are 19'."
Those days at RADA were indeed the turning point. This is where Thaw thawed out, eliminated the gags and learned to listen and show ... humility.
"Things changed," he admits. "Initially a lot of my confidence was knocked out of me. Maybe I realised I wasn't as good as I thought I was. I had a lot to learn. Tom Courtenay was in a similar boat but he had been to university and was a lot cleverer than I was. I was a little intimidated by his knowledge and intellect.
"I went quiet and withdrawn ... that's the way I became. People said they were frightened of me. I appeared to be and was a loner. They didn't know where I was coming from."
Next week sees the return of Thaw to television in Kavanagh QC in which his first guest star, ironically, is the said Mr Courtenay (as an alleged wife killer he defends). This time around he has a brief romantic skirmish with another QC played by Geraldine James - dignified sort of middle-aged sex on a boat. Prepare for Ms James to become a more permanent fixture in the long-term future.
Thaw is relaxing in a hotel overlooking Hyde Park and looking every inch the off-duty QC in a silky, grey suedette jackette, a crisp blue shirt and grey slacks. He's a trifle weighty around the midriff having just had four months off and scoffed a ton of pasta on a break to Venice with his actress wife Sheila Hancock.
Perhaps like James Kavanagh, he deals with a crisis through experience. In one episode of the new series he revisited his roots in the Longsight district of Manchester where they were filming. The memories were powerful.
As a child his mother Dorothy walked out on the family leaving his father John to cope. His parents reconciled and then parted again. He can vividly remember being reconciled with her for 30 minutes before her death in the Seventies.
He says: "We never got close. It was sad. I didn't know she had been ill. It was difficult for my father bringing us up. I didn't feel at all deprived ... it was just that our mother wasn't there."
Fast forward to the late Eighties. His wife Sheila contracts breast cancer. She's a fighter and they face the worst together. She pulls through but the pressure leads to a brief later parting of ways.
He says: "My problem was that I was working so hard the only way I knew then was to give 110 per cent to my work. So I had to adjust. There were more important things in my life than work. This was a threat that the woman you love was going to be taken away from me. I had been too complacent. Thank God things are fine now. But I don't get complacent any more."
Thaw's career has been an upward spiral in neat patterned phases. He employed his earthiness to full effect in movies such as The Bofors Gun and on television in the series Redcap.
In the Seventies he gave us Jack Regan and The Sweeney. In the Eighties he had a spell with the Royal Shakespeare Company.
There was a professional blip when he was miscast as author Peter Mayle in the BBC's A Year in Provence. Typical of the unmoved Thaw, he soon picked up superb reviews for his socialist leader in David Hare's The Absence of War at the Royal National Theatre. That same year, in 1993, he appeared at Buckingham Palace to collect a CBE.
Yet he feels he has under-achieved in terms of the stage. "Most haven't had the luck. I have," he says, munching on a biscuit. "You have regrets. With hindsight I wish I had done more theatre. I am thought of as a TV actor. But I haven't pushed myself as an actor."
He is one of only a handful of actors in Britain who can be genuinely called "millionaires" and command pounds 250,000 a series. There is a large country house near Malsbury in Wiltshire, a pretty retreat he rarely gets to see in Provence and a cosy "working" home in Chiswick, West London.
Thaw enjoys the company of women, which is just as well because there are three daughters - Abigail, 32, an actress from his marriage to history professor Sally Alexander, Melanie, 34, from Sheila's marriage to the late Alec Ross, and their own child Joanna, 23, who has just left Cambridge University and is considering a career behind the cameras directing.
He is about to make a pounds 1m TV film called Goodnight Mister Tom (hence the hair and beard), playing an elderly widower who finds himself landed with a young evacuee from London at the outbreak of the Second World War before he puts in his final appearance as Morse. But there will be more of Kavanagh QC.
Indeed, Mr Thaw is not about to retire gracefully.
"I don't think I can," he says, his blue eyes alive with energy. "I'm a fidget. I can't relax. You can't take an ad saying `John Thaw has retired'. Too many people would laugh."Reuse content