I think you need to look at what the bar tab in this case was - it comprised drinks purchased after Mark was found at a thank you celebration to which the rescue teams who had found him were invited, arranged by British diplomats who had been liaising with the Algerians. It wasnt just Marks personal drinks.
(Just posted the same in a duplicate thread, I created - this one wasn’t there when I started posting, but beat me to the post).
That does seem obvious.
Anyhow, Baroness Thatcher did the right thing. Wonder if Barack Obama would have done it.