By ROBERT HARDMAN

Last updated at 00:13 22 December 2007

Everything is shut. All the pubs have locked up and the last train went ages ago. Las Vegas this is not. I am in downtown Wolverhampton on a Sunday night and the temperature is somewhere below zero.

The place is dead - except for one corner of town which is not merely alive but rocking. And, as the clock passes midnight, there is no let-up in the guffawing and applause here, in the neototalitarian splendour of the Civic Hall.

More than 2,000 people are impervious to the fact that it is now Monday morning. It is well past bedtime for many - this is a crowd of a certain age - but few show signs of flagging.

And they are all captivated by the same comedian who first appeared on this stage back at 7pm and shows no sign of leaving it. What's more, he hasn't uttered a single obscenity all night.

But perhaps the most remarkable thing of all is that this man has just turned 80. And Ken Dodd has absolutely no intention of retiring - or even slowing down.

If you're passing through Hanley in the Midlands at midnight tonight, listen at the door of the Victoria Hall. It will be the same next week if you happen to be strolling past Nottingham's Royal Concert Hall in the early hours - or Liverpool's Philharmonic Hall the next evening.

To his fans, he is a comic genius. To others, he is that bloke off the telly in the Seventies who built his career on his mad hair, his duster (or "tickle stick") and a supporting cast of dumpy midgets called Diddymen. To a lot of younger people, he is, simply: "Ken who?"

But you don't get 2,000 sane people to maroon themselves voluntarily in Wolverhampton at midnight on an Arctic Sunday unless you're something special. To do so at the age of 80 is beyond commendable.

After all, this is a man who has been nominated by his fellow Liverpudlians as the greatest Merseysider of all time, no mean feat in a famously self-regarding city full of pop legends and soccer gods.

He is now a Grade One listed Scouser, elevated beyond the cluttered ranks of mere celebrities to the exalted status of national treasure. On Christmas Eve, BBC2 devotes an entire episode of Arena to the Dodd legend.

"If you don't laugh, I don't mind," he tells the Wolverhampton crowd. "I'll just add another five minutes to the show." We all laugh and the show goes on anyway.

"Doddy' launches into another bloke-visits-doctor gag. "So this fellow tells the doctor: 'Every time I sneeze, I feel very sexy.' The doctor asks: 'What do you take?' 'Pepper.'"

It's not a bad joke. It's not a great one, either. But many people are bent double, for two reasons. First, the delivery and timing are spot on.

Second, it's just part of another volley in a rapid-fire joke bombardment. There is no time to reflect too much on the merits of any gag because another one is already under way. Ken Dodd doesn't do 'boom-boom!' or 'geddit?' He just charges ahead.

If this was being televised, they wouldn't need the bleep machine, even before the 9pm watershed. The show is packed with innuendo, of course, and plenty of oo-er-missus humour which would do justice to a Carry On film. But unlike the average Carry On caper, this is still funny.

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"She was a big girl," he reflects fondly of his first girlfriend. "You could tickle her all night and never touch the same spot."

It might not be hilarious on paper. But, believe me, they are howling, especially when he just keeps piling it on: "She tried the speak-your-weight machine. It said: 'To be continued...'"

It's a line which captures the cleverness of Ken Dodd. The speak-your-weight machine is such an outdated concept from the bygone age of the knotted handkerchief that if it reappeared today it would probably be arrested under the Data Protection Act. But the joke emerges as fresh as any expletive-packed rant about the latest iPod.

I have arranged to meet Doddy before the show in his dressing room. He has told me to ask for him at the front-of-house. He has not told me it will be like a silver-haired pop concert.

The show is a £17-a-head sell-out and they are queuing round the block in the freezing cold. The woman inside the front door cannot talk to me as she is too busy selling Ken's "tickle sticks" to semi-hysterical ladies keen to enter the party spirit.

Even the bouncers - a breed given to boorish self-importance at such occasions - are full of bonhomie. They know the routine for a Ken Dodd evening. It will be impeccably behaved and extremely long. "Ken's always welcome here - whatever time he wants to finish," says manager Steve Evans.

David Prees, 57, has had an hour's drive from Tamworth in Staffordshire to be here. He has been attending Dodd gatherings since the Sixties and expects a late night.

"The latest ever? Oh, that was probably the Alexandra in Birmingham five or six years ago when we didn't get out till 2.30 in the morning. You sometimes hear a few jokes you've heard before, but they're always funny. I've seen Ken more than any other comic. I just like his attitude. And you certainly get value for money."

There's no grand entourage. Anne Jones, Ken's girlfriend, sidekick and support act for two decades, comes out to usher me backstage where the man himself is padding around his spartan dressing room in socks.

He looks much younger than his 80 years - he has became an octogenarian in the past few weeks - and his hair has the same old just-electrocuted look. What does he put in it? "It's natural. It just does what it does."

This is not so much a celebrity dressing room as a council office with a mirror. Does Dodd have any diva-style demands, like those celebrities who have to have pink flowers or a feng shui furniture arrangement? He laughs. "They're very nice here and give me coffee and biscuits but I don't ask for anything. Most of the places I go these days, you have to take your own soap."

Born in the Liverpool suburb of Knotty Ash - where he still lives - Dodd says he had an idyllic childhood. His father was a coal merchant and a natural comedian from whom the boy Ken learned the art of joke-telling.

As a teenager, he bought his own ventriloquist's dummy and went touring local stages, supplementing his wages from his father's coal business. His heroes were local comedians like Arthur Askey and Tommy Handley and, in 1957, he, too, joined the ranks of the professional entertainers.

Within a decade, he was enjoying a record-breaking run at the London Palladium and beating the Beatles to Number One in the charts. He played in front of Prime Ministers and royalty and his appearance in any seaside theatre during the summer would guarantee a sell-out season.

Television turned him into a British institution. Other comedians could raise laughs just by impersonating Ken Dodd.

The comic landscape started to change, though. What were originally known as "alternative comedians" started to become the norm. The traditional variety acts started to fade. Television stars like Mike Yarwood had been giants in the Seventies but by the late Eighties, their sort of stuff was curling at the edges.

Some of them disappeared. Others packed their crumpled dinner jackets and hit the road, spending their summers at the end of a pier and their winters in panto.

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The big television audiences no longer craved an old-fashioned night of "light entertainment" with a few safe song and dance routines, a half-decent magic act and a front man with a few mother-in-law jokes and the same old impressions with the same old props: Harold Wilson (pipe), Denis Healey (eyebrows), Robin Day (bow tie), Eddie Waring (sheepskin coat).

But Britain was a different country then. And that is what I find so impressive about Ken Dodd. He excelled in the heyday of variety, endured the comedy reformation and yet is still going strong.

In 1989, just as his genre of entertainment was falling off a cliff, he was tried for tax evasion. He was acquitted but the publicity, the pressure and the timing of the case might have killed off a lesser funny man. Dodd merely picked up his tickle stick and returned to the stage to find his audience as enthusiastic as ever.

And, 18 years later, they are just as excited here in Wolverhampton as they pile in to the stalls. The majority would probably qualify for a free bus pass but there are plenty who have a long way to go before Saga calls.

In the front row, I find three generations of the same family. Cannock teacher Lisa Pearce, 36, has been a Doddy fan since she first caught him in Bloxwich at the age of 12, and tonight she is here with her mother, June Simkiss, and her 12-year-old son, William.

All are fully equipped with tickle sticks. "I love his humour and the fact that all three of us will laugh at the same things," says Lisa.

It might be a far cry from a Royal Variety Performance at the London Palladium but Dodd is clearly in his element. I had half-expected a trace of ennui, a glimpse of a jaded old pro going through the motions. Not at all.

He genuinely loves every minute on stage - "I'm stagestruck, always have been" - and cannot envisage life any other way. "Retirement is when a man stops doing what he doesn't want to do."

He and Ann certainly like the odd holiday. "We'll have a holiday for the body in somewhere like Tenerife, then a holiday for the mind - like watching circus acts in Munich." But life just seems to be an interval between shows.

"I love these big old halls. They're all different and so are the audiences. You have to play them like an instrument and I can honestly say I've never done the same show twice," he says, buzzing with anticipation, ten minutes before kick-off. Is he nervous? "Of course. I'm like a racehorse in the stalls."

Moments later, the show starts with a few carols from a supporting cast of child performers. It's not much of a warm-up but Ken Dodd doesn't need one. He tells the audience that he's rubbish and they're rubbish but we all know that this is rubbish. They're loving it.

"When I first came in, I thought I was in out-patients. Heavy breathers, go over there. Haemorrhoids? You remain standing..." And he just hoses them down with gags for the best part of two hours.

"How many men does it take to change a toilet roll? Don't know. It's never been done." The routine is peppered with jokes about money and accountants. It's a bit incongruous at first until I remember the court case. Most people would probably rather forget about it - I had imagined that Dodd would, too.

Liverpool is a recurring theme. He still lives in the same house where he grew up and is fiercely proud of his home city's imminent inauguration as European City of Culture. But that doesn't mean it's not a laughing matter: "The dockers are having ballet lessons... I came down the other morning. There was the car jacked up on four encyclopedias."

After about an hour and a half, he makes way for a wartime sing-song. A lot of people head for the bar but rush back when Dodd reappears in his furry red "moggy coat" for another hour and a half.

One or two unfortunates cannot stave off the call of nature and try to slide out to the loos but he's soon on to them. "Am I that bad?" he shouts as a blushing woman makes a run for the ladies.

The interval finally arrives at 10 pm but the star turn has barely got going. On and on he goes. Some of his jokes are from another age - a distant land of coal sacks, pools coupons and beauty contests in Skegness. Who cares? It all makes sense - and nonsense.

Finally, somewhere after midnight, he senses that the moment has come and launches into a parting burst of one of his old hits, Absent Friends. It's shamelessly sentimental. And he does it brilliantly. They give him an ovation. He comes to the front of the stage to shake a forest of hands.

For us, the show is over. For Ken Dodd, it's the beginning of another interval before he is back on in Hanley, Nottingham, Liverpool, Derby, Brecon, Bournemouth...

If he is lucky, he'll be in bed by 3am. Happy 80th, Ken.