A horse that was wearing a curple,
Found the sting of a wasp made him hirple,
Said the horse, "I don't mind"
"But I'm starting to find,"
"That the spot of the sting has turned purple!"
Whenever Giles is on Qi, about half the episode is him going off on an anecdote.
I think it's Brandreth? Not gonna lie, those are some of the best ones. You never know if what he's saying is 100% true because he was there or 100% out of his ass. Either way, you leave entertained.
He left at the end of the 13th season. Not entirely sure why: whether he was getting bored with it or wanted to move on, but I do recall he had some health problems around that time. Possibly a combination.
Sandi Toksvig, the current host, is Danish (she's not subtle about that at all. lol). She was a guest several times when Fry was hosting and took over after his departure. She's lived a, pardon the pun, quite interesting life, so she brings as much to the table as Stephen did.
I think she's doing a great job. It took about half of her first season for her to really hit her stride, but she's definitely in the right chair.