I understand; Top Gear has done it at least once with a motorcycle, but I'm talking about descending bicycles. Given their penchant for racing various cars against skydivers, free falling Volkswagens, bicycles (in rush hour traffic), steam locomotives, free runners, Olympic skeleton racers, jet roller skates, power kayaks, public transportation and whatever else, a time trial down a steep descent with a TdF rider vs. Stig in a 2Smart might be a worthy project.