The passenger steamer SS Peel Castle was operated by the Isle of Man Steam Packet Company from her purchase in 1912 until she was sold for breaking in 1939.

Peel Castle was built as Duke of York at Dumbarton by William Denny and Brothers, who also supplied her engines and boilers.

She was to have 100 officers and crew and was fitted out as an auxiliary, capable of carrying boarding parties and prize crews, and was put under the command of Lieutenant-Commander P. E. Haynes RNR[2] Peel Castle sailed under the White Ensign in January 1915, her engine room manned mostly by Steam Packet Company personnel, and became part of the Downs Boarding Flotilla, a section of the Dover Patrol.

Her crew captured a number of enemy personnel who were trying to get back to Europe hidden in neutral ships, including Franz von Rintelen, an infamous agent of Admiral Tirpitz.

After having been fitted with depth charge throwers and paravanes and with her boat deck extended as a landing for kite balloons, she patrolled north of Shetland.

The war over, Peel Castle was refitted once more, this time as a troop carrier, work she continued until May 1919, after which she returned to Liverpool and resumed her peacetime Steam Packet Company duties.

No apparent damage could be seen so Peel Castle left Douglas the following day, bound for the Graving Dock at Cammell Laird's in order to be inspected by representatives of Lloyd's of London.