The best way to get an idea of just how big of a task each episode of Top Gear was is to read this story by Sniff Petrol and TG script editor Richard Porter. It essentially breaks down how ideas were formulated for each new segment, and then explains how they were built. The almost day-by-day breakdown reveals a number of fascinating things about the show.
The most obvious tidbit gleaned is the reinforcement of the idea that Jeremy Clarkson is a passionate, meticulous workaholic, a trait that only recently bubbled up following the host's firing. In his writing about the TG process, Porter calls Clarkson the "chief scrutineer," who after a day of brainstorming and script writing would often show up to work the next day with "a dozen new script tweaks, suggestions and jokes" after having "lain awake all night worrying over tiny details and agonizing over the smallest point until he'd got it right."
Perhaps most interesting of all the revelations, though, is the planning. It'd often consist of the team sitting around, tossing out ideas and attempting to justify why they need to be done. Porter provides a great example of a failed idea – the team would build a better firetruck – and just why it would have never worked. It's that kind of peek inside the Top Gear brain that makes this a worthwhile read.
Head over to Jalopnik and check it out.