Page "Prime Minister of the United Kingdom" Paragraph 102

Peerages, knighthoods, and other honours are bestowed by the Sovereign only on the advice of the Prime Minister.

The only important British honours over which the Prime Minister does not have control are the Orders of the Garter, Thistle, and Merit ; the Royal Victorian Order ; and the Venerable Order of Saint John, which are all within the " personal gift " of the Sovereign.