Buggins's Turn Meaning

(idiomatic, Britain) 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.

Example:   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) [1]
  I remembered your old saying "Some day the Empire will go down because it is Buggins's turn."'