Lewis Hamilton could not contain his smile as he smashed Sebastian Vettel's lap record on the British motoring television show Top Gear.The 2008 world champion's existing lap of the show's test track in a Suzuki Liana, set on a wet and slippery track some years ago, was bettered by seven tenths by current world champion Sebastian Vettel.Asked if that has irritated him, Hamilton admitted to presenter Jeremy Clarkson: "Uh huh."He's had the best car (in F1) for god knows how many years, and he's also (been) the quickest on top gear," said the Briton.IMPRESSIVE LAPHamilton's new time around the Top Gear test track - actually the Dunsfold Aerodrome in Surrey - was 1min42.9, more than a full second quicker than German Vettel.Clarkson called the feat "unbelievable".Clarkson was, however, less impressed with Hamilton's move from McLaren to Mercedes, comparing it with leaving Manchester United in order to play for West Ham.Hamilton answered: "Everyone is criticising it, but for me, I've been at McLaren since I was 13 and I want a change - I'm a risk taker."NO EXPECTATIONSBut the 28-year-old warned that Mercedes has "really struggled" in the past few years, and so his fans should "definitely not expect" early poles and wins in 2013.Mercedes chairman Niki Lauda, however, told Italy's Griglia di Partenza programme that the performance of the new W04 was "not bad" at the recent Jerez test in Spain."We wanted Lewis Hamilton because he is a phenomenon, but we are also very pleased with Nico Rosberg."Now it's up to us to give them a car capable of winning."