After six weeks globetrotting, driving the world's most jaw-dropping machines, actor Will Mellor and presenter Kirsten O'Brien take on their final, and deciding World's Toughest Driving Test. With the series score level, it's a climactic end and it all comes down to one last race driving the tree harvester - a six-wheeled monster truck with teeth, deep in the Uruguayan forest. It will be a gruelling week for Will and Kirsten and there's one man they need to impress, mentor David Henderson. Scotsman David transformed tree harvesting in Uruguay 14 years ago and nobody is better placed to teach Will and Kirsten the do's and don'ts of modern day tree felling than him. Tough-talking David's regime of lessons and tests will prepare Will and Kirsten for the ultimate head-to-head at the end of the week, but only if they buckle down, listen and learn, fast. Throughout the week, Will and Kirsten believe they have the edge over the other, but an eleventh hour set back puts the final race in doubt as Mentor David drops a bombshell. David's not happy for them to proceed to the race. After driving everything from tanks to dumper trucks, the possibility of not being allowed to race is a body blow to Will and Kirsten. In true fighting form and after one final push, Will and Kirsten convince David that they're capable of handling the awesome tree harvester and the race is back on! Thousands of miles from home and in the searing 40 degree sunshine, the heat is well and truly on as Will and Kirsten desperately battle for victory. But who will be the ultimate winner of World's Toughest Driving Tests?