I make such a point of the presence/absence because I know that most vintage folks I know consider this wide, flapped, "watch" pocket to be one of the hallmarks of a British vintage (pre- mid 1950s) suit. I realised when going through my trousers a few years ago that the opposite seemed to be true, and that certainly before WWII they are the exception, not the rule. Indeed in the Burton's catalogue hbk has a pic from, waistband pockets of any kind are only mentioned in the formal wear section. There is no mention of them anywhere else in any of the large number of catalogues I have looked through. That catalogue also includes a section on instructions to branch managers, which is quite fascinating.
Interesting, all my British suits are from the 1950s (or later). I have one suit (label's been cut away) with the large flapped pocket.
A couple have the non-flapped pocket. (also most of the British formal wear I have seem to have the unflapped pocket)
1954 Austin Reed:
However, some do not have a pocket:
1955 Anderson and Shepard with no pocket:
Late 1950s Burton I just sold:
Thank you gentlemen this has been a most enlightening conversation!