Two Ilkley booksellers were today celebrating a share of more than £5 million after selling a collection of rare paintings by the great English artist, William Blake.

Paul Williams and Jeffrey Bates, of Fine Books, were today sworn to secrecy after the 19 illustrations by the artist and poet were sold at a London art dealers this week.

The pair had been involved in a High Court wrangle over the ownership of the works of art which they found in a Glasgow bookshop called Caledonia Books.

But the booksellers, the Scottish book shop and the original owners have settled the outcome and were today celebrating their massive windfall.

The details of the sale were today shrouded in mystery after all parties signed a confidentiality agreement not to talk about the deal.

Yesterday an apologetic Mr Williams said: "I'm sorry, I can't tell you anything. All the partnerships to the business have signed confidentiality agreements."

The anonymous buyer is believed to come from overseas. Libby Howie, the London art dealer, who negotiated the sale, said: "It is one of the most exciting sales I have been involved with. Everybody was very happy with the outcome and happy that they had resolved their differences amicably and fairly and from my point of view it made it possible to go ahead with the sale."

Miss Howie said the illustrations were the 'Holy Grail' of Blake's work and had sold for 'considerably in excess of £5 million' to an overseas dealer with a large collection of art.

It is not known whether the works will remain in this country or go abroad. They had only been known to exist because Luigi Schiavonetti produced engravings of 12 of the paintings. The originals had disappeared after being sold in 1836.

"This is of the most enormous significance," Miss Howie said. "It's the greatest ever discovery of Blake's work. The assumption was they had been destroyed or lost, but for them to turn up in a neat little folder was astonishing."

Most of Blake's work is in the hands of the great museums in this country and abroad. "There is almost nothing in private hands," Miss Howie said.

The collection, originally valued at £1 million, was rediscovered after 165 years and the Ilkley dealers approached Dominic Winter Book Auctions in Swindon, Wiltshire.

Auctioneer Dominic Winter, who specialises in sales of a wide range of antiquarian and rare books, then contacted various Blake scholars, including Robin Hamlyn at Tate Britain, curator of a Blake exhibition in 2000.

He told Mr Winter that Blake was asked to do 40 drawings for the book but when it was published it contained just 12 designs.

Art expert Shirley Graham at Leeds City Art Gallery said the cache was a valuable find.

"A collection of his paintings all illustrating the same work would fetch a huge amount," she said. "Blake's work wasn't very popular when he was alive and he was poor until the day he died."