Announcing the move late on Friday evening, The Times editor Robert Thomson said: "This is a significant moment in the 216-year history of The Times. The launch of the compact has transformed the fortunes of the newspaper and made The Times even more influential as Britain's journal of record.
"Our talented and committed team of journalists is determined to produce a newspaper that is bringing quality reporting to an ever larger audience and to uphold the traditional virtues and values that have made The Times respected around the world."
The Times had been expected to switch fully to tabloid by Christmas, but the sudden dropping of the broadsheet took many by surprise, including staff on the paper, who were only informed on Friday evening of the move.
One of the major factors in the move is the cost of producing two separate version of the same newspaper, which was believed to be costing Times owner, News International, around £15m a year.
After a regional experiment, which saw sales of the tabloid versions grow by up to 32% after the broadsheet was dropped, senior management were keen to cut the large-format version altogether.
In the Irish Republic, sales of The Times rose by 32%, in Northern Ireland by 22% and by 11% in Scotland when the broadsheet was no longer available.
Paul Hayes, general manager of Times Limited, said: "The move is a response to clear reader demand and we look forward to a compact future."
The Sunday Times ran a full-page ad informing its readers and in the first compact-only version today a letter from the editor on page two is dedicated to the change.
The move comes as the latest newspaper ABC figures show that the paper is going from strength to strength with a third consecutive year-on-year increase.
The Times has reported an increase of 14,536 copies, up 2.28% year on year, giving the paper a circulation of 652,264 with full-price sales up by over 3%.
Sales of the compact are believed to have hit 300,000, representing 46% of The Times' total sales. It had been believed that once readership of the compact edition hit 50%, the primary editorial and marketing focus would switch from the broadsheet to the compact.
In June, Brand Republic's sister title, Marketing, reported that The Times was plotting a major autumn marketing campaign as it switched its editorial emphasis to the compact edition.
The Independent was the first to launch a tabloid version of its broadsheet last autumn and in May this year it went fully tabloid.
The Times timeline
1788 The Daily Universal Register becomes The Times
1805 The Times reports the Battle of Trafalgar on the front page (this issue has recently been picked as one of the front pages of the Millennium by Press Gazette)
1922 First picture page published in The Times
1930 First crossword published in The Times
1932 The Times introduces Times New Roman, the world's most famous typeface
1966 News appeared permanently on the front page for the first time replacing the customary classified advertisements
1981 The Times is bought by Rupert Murdoch
1986 The Times first published from Wapping
1996 Times Online launches
2003 The Times compact launches in London on November 26
2004 The Times publishes in compact format six days a week from November 1
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