He's a television presenter / restaurant critic. I believe he came from Boston (Mass., that is, not Lincs,) but has lived here for quite a time. He talks with an accent halfway between Bostonian and Mayfair, rather plummy, rather drawly. People from both sides of the Atlantic seem to hate his voice. One of his critics described him as "suffering from irritable vowel syndrome"!
If you google for "loyd grossman accent" (NB, only one "l") you'll find page after page of references.
Personally I think people should speak in whatever accent they want, so his doesn't offend me in the least.