David you are quite right there is a button hole lined up with the twin button strap which of course I can just do up, and that was obviously (now you mention it) its original purpose.
Nick the three buckle boots are much earlier than you may think, a friend of mine had a WW1 dated pair a few years ago, the toe was more like the earlier ammo boots without the external cap, they were used by the Royal Engineers but not necessarily for motor cyclists just muddy work.
My size 11 3 buckle boots fit in both of my sets of leggings, but I haven't tried it wearing them.