HMS Monmouth (F235) is the sixth Type 23 frigate of the Royal Navy. She is the seventh ship to bear the name and was launched by Lady Eaton in 1991, being commissioned two years later.
Affectionately known as 'The Black Duke', Monmouth is the only ship in service with the Royal Navy that has its name painted in black and flies a plain black flag in addition to the ensign. This is due to the dissolution of the title and the blacking out of the Coat of Arms of the Duke of Monmouth in 1685 following the Monmouth Rebellion against James II of England.
Information courtesy of Wikipedia