The British Prime Minister, Mr Blair, led tributes yesterday to Viscount Rothermere, who changed the face of British journalism and died on Tuesday night at the age of 73.
With Sir David English he relaunched the Daily Mail as a tabloid newspaper, providing a voice for middle England.
As tributes poured in from the industry and politicians, Mr Blair spoke of his sadness at the death of the peer, who switched his political allegiance to New Labour.
Mr Blair said: "He was an extraordinary man, and underneath that very bluff exterior was a sharp mind and a very kind personality."
Two former Conservative prime ministers, Baroness Thatcher and Mr John Major, also praised him.
Lord Rothermere, the proprietor of the Daily Mail, Mail on Sunday and Evening Standard, died at St Thomas's Hospital, London, after a heart attack. He had been in good health and had just flown in from France, according to the Daily Mail and General Trust company.
His son and heir, Mr Jonathan Harmsworth, managing director of the Evening Standard, was at his bedside, a spokesman said.
He also leaves, from his first marriage, two daughters, Mrs Geraldine Maxwell (40) and Mrs Camilla Yeates (34), and a stepdaughter, Ms Sarah Holcroft.
A year after the death of his first wife in 1992, he married Ms Maiko Joeong-shun Lee from Japan.
Lord Rothermere had sat as a Conservative since inheriting the title from his father in 1978, but joined the Labour benches in the House of Lordsin May last year.
Although the Daily Mail and Mail on Sunday had backed the Conservatives in last year's election, the Evening Standard supported Mr Blair.
Lord Rothermere was the scion of a newspaper dynasty founded by the pioneer of popular journalism in Britain, his great-uncle, the first Lord Northcliffe.
He relaunched the Daily Mail as a tabloid after the old broadsheet had been on the verge of extinction. Eleven years later, in 1982, he launched the Mail on Sunday.
The career of Vere Harold Esmond Harmsworth, the son of the 2nd Viscount Rothermere, began in a Canadian paper mill before he joined the family firm in 1951. He assumed control in 1971 at a crucial time, with the Daily Sketch in decline.
He closed the Sketch and appointed its editor, Sir David, editor of the Daily Mail.