I think it is just a running joke. The actual person probably varies; all are 'pro-race' drivers of a certain ability. By creating the fun mystery; the show has circumvented the possible accusation that their ratings are subject to (various) driver ability.

As an ex-pat Brit now in SoCal; I do miss Top Gear and the fabulous humour.

No disrespect to Americans (I love your country) - but check out the video of "Richard Hammond in a big Dodge Charger" on the video section at
Top Gear

A funny, wry and brutally honest review of an all American classic.

And check out the 'tiny' Brit garages !!!! :

Darn it; getting an X into a standard Brit garage must be tough.

PC