They're almost unique in showbiz for the length of time they've been around and yet never really hit a stale patch. Even when a show was a bit rubbish (and a few were), it was the show that suffered, not them. It says so much about them. They have the genuine X-factor, something that can't be manufactured (note to Simon Cowell) and that's what makes them so enduring. They're talented, clever, very funny and very grounded and that's always going to generate real affection.