Journalist and broadcaster John McCririck has died aged 79, his family has announced.
McCririck is survived his wife of 48 years, Jenny.
Ascot Racecourse has released a statement saying it is "deeply saddened" by the death of McCririck.
"Everyone at Ascot is deeply saddened to hear of the passing of John McCririck," it tweeted.
"He was an unmistakable presence in racing, and one of the most impactful broadcasters of his generation."
A statement released by John McCririck's family said: "Award-winning journalist, broadcaster and for many years the face of British horse racing, John McCririck, passed away at a London hospital on Friday, July 5 aged 79.
"John's interest in horse racing and betting began at Harrow where he was the school bookie. On leaving he worked for an illegal street bookmaker then legally on-course where he learned the art of tic-tac, clerking bets and making a book.
"John cut his teeth in racing journalism on 'Formindex', a tipping sheet otherwise known as 'The Golden Guide'. He went on to write for the Sporting Life where he won British Press Awards, 'Specialist Writer of the Year' and 'Campaigning Journalist of the Year'.
"John joined ITV in 1981 for Shergar's Derby then became a household name as part of the Channel 4 Racing team when they took over coverage of the sport in 1984.
"His flamboyant broadcasting style from the heart of betting ring proved extremely popular with racing fans and beyond.
"John continued to work for Channel 4 Racing until 2013, as well as satellite channel At The Races.
"In this time he transcended the world of racing, appearing on numerous mainstream TV news and light entertainment programmes including Question Time, The Weakest Link, Celebrity Wife Swap and Celebrity Big Brother in 2005 and 2010.
"Despite suffering ill health in recent months, John continued to make several TV and radio appearances.
"He is survived by Jenny, his wife of 48 years. His funeral will be private."
BBC horse racing correspondent Cornelius Lysaght described McCririck as "a one-off".
He tweeted: "John #McCririck has died; racing pundit, TV personality, award-winning investigative journalist, 'failed' (his word) bookmaker, showman, rent-a-gob, 'marmite' character, the list goes on & on... unquestionably a one-off."