Thing is, Doug, the two-abreast ding-dong we've been having started with this:

"But if you are two cyclists side by side on a narrow road ..." That's not quite the same thing as a peloton! Of course I've seen the latter and I've been stuck behind. Two things there: first, it isn't easy, and possibly quite dangerous, for ten or twenty cyclists to be constantly falling into single file. Secondly, look at Thomson's video again. Particularly on narrower roads, it's safer and quicker to overtake a bunch riding two abreast than to squeeze all of them into the gutter to overtake them in single file. On narrow or winding roads round here we have to put up with slow milk tankers, tractors and horse boxes (and 97-year-olds in Honda Jazzes) as well as occasional bunches of cyclists (even a single cyclist can slow you down for hundreds of yards round here). Who's going to say which of those road users, holidaymakers' cars included, have more right to be there...?