Join in the celebrations as HMS Belfast marks her fortieth anniversary in London.
She opened to the public on 21 October - Trafalgar Day - 1971.
Nearly eight million people have walked the decks of the ship since she was permanently moored on the Thames.
The ship's company is planning a 40-gun salute, which is sure to make a very big bang, and if you cast your eyes up to the masthead, you'll see special messages being signalled in flag semaphore.
The 40-gun salute will last for seven minutes.