Former England, Watford and Aston Villa manager Graham Taylor has died at the age of 72.
A statement from his family said: "With the greatest sadness, we have to announce that Graham passed away at his home early this morning of a suspected heart attack.
"The family are devastated by this sudden and totally unexpected loss.''
The Football Association said it was "deeply saddened" to learn of Taylor's death.
Rest in peace, Graham.
Our thoughts are with his family, friends and loved ones. pic.twitter.com/jt4zFLTPRi
- England (@England) January 12, 2017
Professional Footballers' Association chairman Gordon Taylor said: "He was a real quality human being.
"He cared about his fellow pros and the good of the game and should be remembered as a man who added to the game, who really showed his ability as a manager.
"He thought a lot about the game and was in his own mould. I'm proud and privileged to have been able to call him a friend."
Taylor began his managerial career at Lincoln City, having played for them and Grimsby.
He guided Lincoln to the Fourth Division title in 1976 and later managed Watford, Aston Villa and Wolverhampton Wanderers.
Dion Dublin, who played for him at Villa, told the BBC he was "completely shocked" by the news and added: "He was a very, very funny man. He had my utmost respect and was a pal as well as a manager.
"When I played under him at Aston Villa he taught me so much. He was very understanding. It is quite devastating news."
- Aston Villa FC (@AVFCOfficial) 12 January 2017
It was at Watford, under the chairmanship of pop star Elton John, that Taylor made his name as he guided what was then an unfashionable club from the fourth tier of English football to the top flight in five years.
Writing on Instagram, Sir Elton said Taylor had been "like a brother" to him and added: "We shared an unbreakable bond since we first met.
"We went on an incredible journey together, and it will stay with me forever.
"He took my beloved Watford from the depths of the lower leagues to unchartered territory and into Europe. We have become a leading English club because of his managerial wisdom and genius.
"This is a sad and dark day for Watford, the club and the town. We will cherish Graham and drown our sorrows in the many brilliant memories he gave us."
Taylor took Watford to the FA Cup final in 1984 -- where they were beaten by Everton -- in a decade-long spell in charge between 1977 and 1987.
He also had a second spell at the Hornets, leading them into the Premier League in 1999 after back-to-back promotions.
Watford chairman and CEO Scott Duxbury said on the club's Twitter page: "As one, together at our club, we are all utterly devastated to learn of Graham's passing."
- Watford FC (@WatfordFC) January 12, 2017
Taylor took Aston Villa from Division Two to top-flight runners-up in the 1989-90 season and was appointed as England manager soon afterwards.
But his spell with the national team was less successful and he resigned in November 1993 after failing to qualify for the following year's World Cup.
Before retiring from management, Taylor spent a brief second spell at Villa in 2002 -- a return he later said he regretted.
He then became a pundit, working on both radio and television, but found time to return to Watford as chairman from 2009 until 2012, with a stand at the club's Vicarage Road ground being renamed in his honour in 2014.
Taylor is survived by his wife Rita and daughters Joanne and Karen.
Information from the Press Association was used in this report.