A historic First Folio edition of Shakespeare's plays was yesterday snapped up by a book dealer for £2.8 million at auction.

T h e "remarkably untouched" 17th Century volume, which probably cost just 20 shillings when printed in 1623, went under the hammer at Sotheby's in London.

A spokeswoman said the lot was bought by Simon Finch Rare Books, of Mayfair, and added that the sale price of £2,808,000 had included the buyer's premium.

About 750 copies of the First Folio - which has been described as the most important book in English literature - were originally printed.

However, only about a third of them have survived to the present day and most of those are incomplete.

The First Folio, published just seven years after the Bard's death, contains 36 plays, 18 of which had never previously been printed.

Experts believe those 18 plays - including Macbeth, Twelfth Night and Julius Caesar - may have been "lost to posterity" were it not for their appearance in the First Folio.

The copy on sale yesterday was described as one of the "two finest" to appear at auction in London since the Second World War.

It was sold alongside other lots at Sotheby's sale of English literature and history in New Bond Street.

The world record auction price for a printed book was set in 2000 when the illustrated four-volume The Birds of America by John James Audubon sold in New York for $8.8 million (£4.8 million).

A copy of Chaucer's The Canterbury Tales holds the record for a work of English literature. It sold for £4.6 million in July 1998.

The nearest comparable copy of Shakespeare's First Folio to go under the hammer sold at Christie's New York in 2001 for $5.6 million (£3.04 million).

Sotheby's said the copy sold yesterday was enhanced by "extensive" markings and annotations, including a number made by a single reader, probably in the 1600s.

The book, which also still retains its 17th Century binding of plain brown calf, was put up for auction by one of the oldest libraries open to the public.

Dr Williams's Library in London was set up in the early 18th Century under the will of a Presbyterian minister.

It held the First Folio edition from at least 1716, making the copy the longest held by any public library in the world.

Library director Dr David Wykes said: "The sale will secure the finances of the library and safeguard our important historic collections of manuscripts and printed books for future generations."

Peter Selley, Sotheby's English literature specialist, said: "William Shakespeare has had an impact on the artistic imagination, on language, literature and all the performing arts, more profound and more widespread than any other writer who has ever lived.

"The First Folio preserves 18 of his plays, including some of the most major, which otherwise would have been lost.

"Relatively complete copies of the Folio in contemporary or near contemporary bindings very rarely come to the market.

"There is only one copy recorded as remaining in private hands."

Other lots at the sale included a first collected edition of Shakespeare's Poems, published in 1640, which sold for £68,400 and a first edition of James Joyce's masterpiece Ulysses , which sold for £30,000.

A Sotheby's spokesman said the price paid this morning was the highest for a First Folio of Shakespeare at auction in the UK, and the most valuable printed book ever sold at Sotheby's in London.