Buggins's turn

Earliest recorded use is by Admiral Fisher, later First Sea Lord, in a 1901 letter.

'Buggins' is a humorous invented surname, suggestive of a man of mediocre ability.

(idiomatic, British) A humorous, disparaging term for the appointment of a person by rotation or promotion, on the basis of length of service (it being that person's "turn") rather than merit or level of qualification.
He will be appointed on the principle of Buggins's turn.
- 1919, Memories, John Fisher (reprinting a 1917 letter to him from an unnamed Privy Councillor)
  I remembered your old saying "Some day the Empire will go down because it is Buggins's turn."'

English