LONDON (AFP) - Queen Elizabeth II celebrates her 83rd birthday Tuesday, which will be marked by a 41-gun salute in central London.

The monarch is expected to spend the day at Windsor Castle, her favourite residence just west of London, with husband Prince Philip.

The 41-gun salute will be fired by six World War I guns drawn by Irish draught horses in Green Park, next to Buckingham Palace.

Despite her age, the queen shows little sign of slowing down -- she carried out 417 engagements in 2008, her 56th year on the throne.

Philip, meanwhile, became the longest-serving consort in British history last week, having spent 57 years and 71 days in the role. The 87-year-old overtook a record set by queen Charlotte who married king George III in 1761.

The queen's birthday is celebrated on two dates -- her actual birthday is April 21, while her "official" birthday is on a shifting date in June, which is celebrated with a lavish horse parade through London.