PC Mick Wass, his rider during his time at the Met, said, "Chiswick has always liked to think he is the one in charge, but he has always looked after me."
Jeanette Allen, Chief Executive of The Horse Trust, said: "Chiswick is a real hero and it is a privilege to be able to provide him with a dignified retirement after spending a lifetime bravely serving the people of London."
More top news
Labour leader Jeremy Corbyn was unable to provide the cost of his party's key manifesto plans on free child care.
Montana Abdhou was with a group of friends when two men on bikes opened fire.
BA is expecting to run a full schedule on Tuesday from Heathrow and Gatwick but said it still had work to do reuniting bags with passengers.