If the sight of him coming on stage with two plastic dogs clamped to his legs, singing "The only thing that looks good on me is you" throws the switch in your brain that leaves you helpless with mirth, you're on. If, on the other hand, you're left asking plaintively: "Why is this funny?" a la Margot in The Good Life, you're probably not destined to be a disciple.
I was a comparatively late convert; I'd missed his early radio shows and tours, but friends who'd seen him live described the spectacle in awe-struck tones. Then, when I caught his first series on Channel 4, I saw instantly what they'd been gibbering on about. Here was someone who could effortlessly create a parallel world to the one we ordinarily inhabit.
In the same way that The Fast Show's catch phrases accrue, over the weeks, into a kind of seamless whole, so Hill's cut-up routines and oblique non-sequiturs - "What are the chances of that happening, eh?", or "Oh Mr Lemon, why are your juices so sharp?" - acquire their own logic.
But the main thing that makes Harry Hill so appealing is the fact that his comedy springs from a kind of benevolence. While sarcasm, rage and humiliation have been the sources of comic inspiration for everyone from Basil Fawlty to Blackadder, Hill proves that you can get through half an hour without trashing or lashing out at anyone or anything.
Even when his comedy flirts with racial stereotyping - he's recently acquired a mail-order Filipino wife, May Sung, whose mission in life is to get her hands on his Abbey National book - his genial, quizzical presence at the centre of things maintains the material's air of harmless innocence.
Any intensity in Hill's persona is turned back on himself; with his neck- swallowing collars, elaborate squint, shiny pate, and obsessive humming and hawing, he resembles a kind of wired big-baby savant (having trained and practised as a doctor at St George's Hospital in Tooting, he's presumably acquired a certain empathy with the wilder extremes of the human condition).
It's no wonder that kids, who can spot a phoney a mile off, accept him as one of their own.
In short, he's conquered the world - or at least, that portion of the world, myself among them, which has been cancelling engagements to get home for 11pm on Fridays - by being delightful. What are the chances of that happening, eh?
`Harry Hill's Christmas Sleigh Ride' will be broadcast tomorrow at 10.30pm on Channel 4Reuse content