There was some very clever scheduling for series 12 as it ended with a special challenge edition that was broadcast during the 2008 Festive season. With an epic eight day road trip across Vietnam planned, our daring trio excitedly set out in search of cars with their extravagant-sounding budgets. Unfortunately for them, the exchange rate wasn't quite as good as they thought and so their only option was to invest in motorbikes or mopeds. For Clarkson, who, unlike his pals loathed bikes, this was particularly bad news. Slow, bumpy, tiring, hot and humid - these were the more polite descriptions they gave of the journey, but in between breakdowns, arguments and injuries (the novice came off his bike during a spectacular slide), they witnessed breathtaking scenery, sampled fascinating recipes, learnt a lot about Vietnamese culture, interacted with wonderful locals, bought each other ridiculous gifts and had outlandish suits tailor made. Oh, they also cheated and piled onto a train, only to end up in the wrong destination. With such an outstanding conclusion, the rest of the season could have been rubbish and we would have forgiven them, but nothing could be further from the truth. The team made a second trip to the US, this time to test out muscle cars - and once again failed to make friends with our American cousins; Richard and James found themselves on the French Riviera to pit a Ferrari Daytona against a powerboat; Jezza almost ‘went green' during an electric car test; and in the One Tank Challenge, the trio raced in a very unfamiliar style, each trying to make it from Switzerland to Blackpool without an additional fill-up. Celebrity guests included Michael Parkinson, Mark Wahlberg, Will Young, Harry Enfield, Boris Johnson, Tom Jones and Kevin McCloud.