Quarterdeck is a Regency era manor-house on the edge of Windsor Forest occupied by M. M is served there by his faithful valet Chief Petty Officer Hammond, who served him likewise in the Royal Navy before his retirement to head MI6.
In On Her Majesty's Secret Service, James Bond visits M at Quarterdeck after obtaining information on the whereabouts of Ernst Stavro Blofeld. M is seen inside preserving samples of rare butterflies, a hobby of his.
- The name "Quarterdeck" comes from the naval term for the raised deck behind the main mast of a sailing ship. Traditionally it was where the captain commanded his vessel and where the ship's colours were kept.