Tributes are being paid to a cat credited with helping save the lives of Royal Navy officers during the Chinese civil war in 1949.
Simon the cat was buried with full military honours
Simon protected food stores from an infestation of rats on board the HMS Amethyst during a siege.
He was posthumously awarded the PDSA Dickin Medal, the charity's animal equivalent of the Victoria Cross.
The ship's Commander Stuart Hett is to lead a wreath-laying ceremony at the Essex cemetery where Simon is buried.
Simon was awarded the Dickin Medal for bravery, instituted in 1943 by Maria Dickin CBE, the founder of veterinary charity the PDSA, and was given the rank of Able Seaman.
He suffered severe shrapnel wounds when HMS Amethyst came under fire in a 101-day siege known as the Yangtze Incident in which 17 marines were among the dead.
He received a hero's welcome when the ship returned to dock in Plymouth on 1 November 1949.
Simon died in quarantine three weeks later and was buried with full military honours at the PDSA Animal Cemetery in Ilford, Essex.
The Royal Navy said Simon boosted the morale of sailors
Cdr Hett was appointed to sort through hundreds of pieces of fan mail that arrived after news of Simon's service spread.
He said: "Simon's company and expertise as a rat-catcher were invaluable during the months we were held captive.
"During a terrifying time, he helped boost the morale of many young sailors, some of whom had seen their friends killed."
The ceremony marks the day the ship's mission ended.
Simon is the only cat among 62 animals to be awarded the Dickin Medal. Other recipients include messenger pigeons, horses and dogs.
PDSA director general Marilyn Rydstrom said: "The power of animals to support and sustain morale in times of conflict can never be underestimated."