Today's idle curiosity: a century ago, if you wanted to leave London in a hurry and go far away, would there be a ship *tomorrow*?
Quick count of ads in one paper: between 11/4/1923 and 21/4/23 there were eleven passenger sailings from London to India/Australia/the Far East. Eight to the US/Canada/Caribbean. Double that easily if you took the train to Liverpool or Southampton and met your ship there.
@LucasWerkmeister honestly was more thinking of the bit in the novels where the detective says "we'll be watching the ports, he can't get far...'