Mac_Doc came up with this idea first, after his recent 800 mile drive. The X351 is not a common car, so you don't see many about. I recently did a 250 mile round trip via the M25 and M3, and only saw one on the way out and one on the way back. It might be worth posting when you see one, as it might be someone on this forum.
(PS. Downing Street/Westminster doesn't count!)
(PS. Downing Street/Westminster doesn't count!)