He was a doctor of medicine I think who gave it up to become a comedian. The persona is a sort of 'well meaning idiot everyman', but as far as I see, it's very much based on an old, now forgotten TV comedian from the 1960s called Harry Worth. He's just dusted down the format.
It's in the 'family-friendly reaction against satire' mode, like Mr. Bean.
But does it make people laugh? I'd be willing to bet the European mainlanders will call it 'genius'.
I was occasionally obliged to watch his "TV Burp" programme. Given the resources he had, it should have been much, much funnier. Like another comedian whose success continues to mystify me (Russell Howard) the programme comprised clips from other sources - in Hill's case the week's TV, in Howard's case the internet - and alleged funny commentary thereupon.
I've worked with many people who would be much funnier given the same material, and that's in the insurance industry, for pity's sake.