Everyone knows Ken Dodd's act, right? The buck-toothed buffoon, waving his tickling sticks, talking to Knotty Ash's Diddy Men and nattering on about how tattyfilarious life is.

Well, yes. And no. There's a lot more to Doddy that you'd expect. And when I say a lot more, that's exactly what I mean.

For where many younger comics struggle to limp past the 60-minute mark and call it a full-length show, 73-year-old Dodd could talk all night. And he does. He took to the stage of Reading's Hexagon Theatre at 7.30pm and came off at 10.15pm. For the interval.

The Ken Dodd Laughter Show finally came to a halt at 12.45am - five and a quarter hours after it started. Even allowing for two very unfortunate musical turns, and the interval itself, Dodd was telling gags for three and half hours. And since he managed up to six gags a minute - that's a hell of a lot of material.

Impressive statistics, for sure. But what of the material? In that time how many times did he rattle out such well-worn catchphrases like 'how tickled I am' or 'what a wonderful day for..'? Once.

You cannot fail to be impressed by the man's sheer craftsmanship - the sort of skill only half a century on stage can bring. He never once lost the audience, from either fatigue or a misfired joke. Even though the occasional punchline was almost inaudible, you still hung on his every word.

The show has its faults, and plenty of them to the modern ear. But it didn't really seem to matter. And certainly Dodd's audience - of which the vast majority were certainly of pensionable age - had no gripes.

I must admit I never thought I'd be quite so impressed. I went with a completely open mind, but my heart did sink when a naff two-piece cabaret band struck the opening chords of 'Happiness' and the self-styled Squire Of Knotty Ash stomped on, wiggling his feather dusters between his legs, to the obvious delight of most the audience.

Yet, after running through the niceties of his catchphrases, Dodd quickly hit his stride.

Certainly, plenty of the material seemed old-fashioned, rather than just plain old. Dodd relies on the audience sharing his common comedic language of the saucy seaside postcard or Carry On film as a kind of accepted shorthand. Women are busty beauties or sour battleaxes, vicars are easily shocked prudes - that sort of thing. And there was plenty of knob and tit gags in thinly disguised double entendres. Which, I'm ashamed to say, worked very well.

Other references, too, dated him. Demis Roussos's fame didn't outlast 1976, yet he still made an appearance. But, in fairness, others were more up-to-date: John Prescott's punch and Pokemon.

The variety element didn't help either. You could easily imagine Vic Reeves announcing 'Britain's leading lady trumpeter'. But here she was in irony-free person, fresh from a cruise ship, and she 'entertained' for half an hour.

Dodd, too, indulged. He appeared for one mercifully short segment in silly cat and furry coat, wittering on about 'Ticklemas Eve', he sang the truly saccharine ballad 'For The Children and later returned with Diddy Man Dickie Mint for a tired old ventriloquism routine. He even broke off for a series of announcements of birthdays in the audience. The fact we were congratulating Mabel and Nellie perhaps indicating Dodd's demographic.

All very cheesy, as was his unsubtle habit of inserting the word 'Reading' into every other gag to ingratiate himself with the home crowd - who, it has to be said, willingly lapped it up.

Yet the show avoided this light entertainment hell, thanks to Dodd's continual switching of styles.

He was at his best when talking - as a stand-up two generations younger would - about himself and his own experiences. His frequent gags about the taxman packed an added punch because we know the background. And the funniest moments come from the self-deprecating gags about the length of the show ('a feast of fun - and a challenge to the kidneys').

And then, of course, there are the puns. Sprightly wordplay surfaces at every opportunity, building into an unstoppable machine, grinding down every resistance. By the end, you're laughing hardest at things that just don't make sense, yet it doesn't seem to matter. Suddenly lines like 'I loved that little china donkey. It only had three legs and one eye, but you could tell it was a donkey' seem the funniest gags in the world.

And that's Dodd's strength. You're always with him, and eventually he will break down your resistance. It's the sort of stagecraft every comic should study. I've lost count of the number of comics I've seen go along the front row asking punters what they do for a living, but seeing Dodd do it with such lightning and genuine wit (and without ever being cruel - that wouldn't be his style) is astoundingly impressive.

You clearly don't have a long a career as Dodd simply by relying on a few naff catchphrases. Where most entertainers his age might be happy slinking off into semi-retirement, Dodd is still relentlessly gigging, demonstrating night after night that he has mastered the art of stand-up like nobody else has - or probably ever will.