Former Conservative prime minister Sir Edward Heath has died at the age of 89.
His successor Lady Thatcher said he was a "political giant" and "in every sense the first modern Conservative leader".
Sir Edward, who was knighted in 1992, won his first seat for the Tories in Bexley in 1950 and led the 1970-74 Conservative government.
He took Britain into what was then the European Economic Community, but lost his leadership of the Tory party to Margaret Thatcher in 1975.
Lady Thatcher said he was the first modern leader for the party, "by his humble background, by his grammar school education and by the fact of his democratic election".
Prime Minister Tony Blair said: "He was a man of great integrity and beliefs he held firmly from which he never wavered.
"He will be remembered by all who knew him as a political leader of great stature and significance."
Earlier on Sunday Sir Edward's spokesman had revealed he was gravely ill and receiving medical attention at home.
The former premier had celebrated his 89th birthday with a party at his home in Salisbury a week ago.
Sir Edward's term in office was blighted by industrial action and problems with the economy.
With the country on a three-day week and rubbish piling up in the streets, the miners threatened to bring his government down.
Industrial unrest, combined with economic difficulties, led to the Tories being pushed from power in February 1974.
Sir Edward never forgave Mrs Thatcher for ousting him as leader and refused to serve in her cabinet.
Sir Edward, seen with prime minister Harold MacMillan, retired in 2001
When asked in a TV interview if it was true that when Mrs Thatcher was herself deposed he said "rejoice, rejoice," he joked: "I think I said it three times."
After more than 50 years as an MP he retired from politics in 2001.
His former colleague Lord Walker said history would "give him a high rating", adding that he was a "very great man and an enormous patriot".
Former Labour chancellor Denis Healey said Sir Edward had been a friend for many years after the pair met at Oxford University.
"I liked him very much and I think he represented the sensible wing of the Tory Party but of course like others, Ken Clarke and Geoffrey Howe in particular, they could just not win over the extreme right-wing Conservatives."
In 2003, Sir Edward's health deteriorated while he was on holiday in Austria.
He was being treated for a minor stomach upset at Salzburg's main hospital when tests revealed he was suffering from a pulmonary embolism - a blood clot on the lung.
Sir Edward, a bachelor, was famed for his love of music and sailing, in which he competed at international level.