The next night, however, saw Dennis back in his home town of Liverpool playing the less salubrious confines of Croxteth British Legion. Such, then, were the vagaries of life for the northern English working man's club comic in the 1960s and 1970s.
At their peak, such spit and sawdust institutions as Croxteth British Legion were bread and butter for acts like Dennis, especially after Saturday night TV show The Comedians turned the likes of Bernard Manning, Frank Carson into stars. But the rise of the 1980s wave of alternative comedy put paid to these boom years with right-on abandon, and soon the clubs themselves started to close.
This is the back-drop to Jigsy, a new play by TV producer and comic historian Tony Staveacre, which puts Dennis in the solo spotlight as a clubland veteran mourning the demise of such fun palaces. Yet, while Dennis may have played a few of the real-life dives on the circuit Jigsy frequents, character and performer couldn't be more different.
"Jigsy's pre-stand-up," Dennis explains. "The play is set in 1997, which was the time when working men's clubs were beginning to dry out. He's a dinosaur, is Jigsy. He can fill a club in his home town, but any-where else couldn't get arrested."
Dennis reels off a list of names of his comic heroes who barely got a look in on TV, but in the working men's clubs remained kings.
"Jackie Hamilton is kind of a template for Jigsy," says Dennis. "He's someone who started getting up in his local for beer money, then found out he was really funny. It touched a nerve for me, this play when I first read it, because there's lines where I talk about people I've worked with, like Eddie Flanagan, but no-one's heard of him now."
For Dennis, the allure for this world came from an early age.
"When I was a kid I loved watching the shows," he says. "My hero was Jimmy Tarbuck. He went to the same school as me, his dad was a bookie like mine. I started thinking that maybe I could do that. My mum worked at British Aerospace, and through her I started doing a slot at the Nor Green Social club in Norris Green in Liverpool, where I'd come on and do 10 minutes between acts.
"When I first started, it was, 'Oh, he's only young, give him a chance', but then it got harder. Audiences would be sitting there expecting some 40-year-old wearing a big bow-tie, and I'd turn up aged 17. The aw factor was gone."
Still in his teens, Dennis' routines were on radio, and in 1974, he won talent show New Faces, before tea-time impressionists show Who Do You Do? Here he formed a professional partnership with Dustin Gee. The pair became a highlight of Russ Abbott's Saturday Madhouse, and were tipped to be the next Morecambe and Wise before Gee collapsed onstage and died.
By that time, the comedy world had changed. "In the 1980s old-school comedians had to keep their head down," Dennis remembers. "They were seen as people wearing golf trousers who were somewhere to the right of Attila the Hun."
By that time, while Dennis dovetailed between The Les Dennis Laughter Show, The Russ Abbott Show and 15 years hosting Family Fortunes on TV, he had also moved into theatre. While he could and still can mix it up in high-profile blockbusters like Chicago and Me and My Girl, Dennis' first formal stage role was in David Hare's very serious play, Skylight. It was, says Dennis, "a baptism of fire".
He has also acted in Goldoni's The Servant of Two Masters, JB Priestley's When We Are Married, and last year appeared in Alan Ayckbourn's Drowning on Dry Land.
But there were times, like when he did hit play, Art, with Christopher Cazenove and John Duttine, when he felt out of his depth. A public meltdown following the collapse of his marriage to Amanda Holden and an ill-advised stint on Celebrity Big Brother benefited Dennis's career via an appearance on Ricky Gervais's self-reflexive TV comedy, Extras.
With another Gervais-enabled appearance in controversial sit-com, Life's Too Short, unlike Jigsy, Dennis managed to reinvent himself.
"It would have been easy to get trapped there," he says of the clubs he played for 15 years, "but then, there are guys who have brilliant careers there."
Jigsy, Assembly Rooms, August 1-26 (not 13) www.arfringe.com