Twist to the story
My brother Richard says that there is an interesting further twist to the story, which he heard. According to this version, Pierre Chatelanat won a lottery while they were all in Ottawa. He invited the others to join him on a trip through the USA. They got as far as Nevada before their money began to run out. Charles was having a punt on a gaming machine and struck the jackpot. They once again pooled the money and agreed to extend their visit to Mexico.
While they were in Mexico City Charles and Pierre had a bet about some fact or issue they could not agree on. There was no Google to consult, so Charles headed off to the British Council were he was told there was a library. And at the library, there was an attractive librarian called Betty…
As Richard says, there is no way of knowing whether this story is apocryphal or not, but in a number of ways it seems plausible. Why would Charles have gone to borrow a book when he was on holiday and presumably intending to return to England in the fairly near future? Anyway, I like the story because it adds another dimension of implausibility and luck to the narrative of how Charles and Betty came to meet.