Full review: br br Mercedes SLS AMG timed lap - Auto Express Performance Car of the Year br br Building a supercar from scratch isn't easy, but Mercedes's in-house tuning arm, AMG, has an ace up its sleeve. br br As with the original 300 SL, which wowed the motoring world 55 years ago, the doors are hinged at the top and sweep dramatically upwards -- the Gullwing is back and it's landed in the UK.