Haye has had a phenomenal career so far imo. When turning pro he took tough fights against the likes of Arthur Williams and Carl Thompson. He was EBU holder in 16 bouts before travelling abroad in his 21st fight to beat the linear champ after getting up of the canvas. Unifies 3 of the 4 major belts in his next fight and beats the behemoth Valuev to lift a slice of the WW crown. Let him get a soft defence in and ratchet up more UK support so that when a Klit fight does come of it can be held in the UK
Chagaev would have to do a blood test before the BBBofC would let him fight in Britain because he has failed them in other countries. He says he doesn't have Hep but has failed every independent blood screen he's taken. If there is "reasonable doubt" over a fighters health his opponent or the BBBofC can request blood work, Chagaevs history is more than enough to prompt testing.
I wouldn't expect or want him to anyway really, just making the point that Sprott and Rogan are at least as credible as Harrison.