Well, it’s meant to be funny, of course (the intimation being that in the days of the Empire, it was an honour to be jailed by the British!). This is from a classic British TV comedy series that revolves around an incompetent prime minister and the guy who really calls the shots – his cabinet secretary, Sir Humphrey. I don’t think there’s any real honour abbreviated to JB, so maybe this was supposed to be an in-joke at Westminster? Sir Humphrey’s whole line in the dialogue is:
Hacker (the prime minister): JB?Sir Humphrey: Jailed by the British. Gandhi, Nkrumah, Makarios, Ben Gurion, Kenyatta, Nehru, Mugabe, the list of world leaders is endless, and contains several of our students.