There are a handful of folding bicycle brands worldwide. The British seem to be particularly smitten with them with the Moultons and Bromptons. The Brompton is rather like the Mini Cooper of the bicycle world. I've seen photos of Bromptons with Brooks Pro saddles and drop handlebars.
The Brompton races are not just a bunch of goofy guys getting together to drink beer and do something silly (re: cyclocross racing). These are sanctioned races, albeit with a couple of typical eccentric British quirks - attire must be street shoes, collared shirt and tie, and dress jacket. The young men in shorts may be in legal attire, but they are certainly sitting astride a folding loop hole. And they are trailing the banker who by my guess has at least three last names.