BASEL, Switzerland (AFP) - British jeweller Graff unveiled on Thursday what it described as the "most valuable watch ever created" - a timepiece replete with more than 110 carats of diamonds costing US$55 million (S$70 million).

Unveiled at the watch industry's biggest annual tradeshow, BaselWorld, the glittering wristwatch, called "Hallucination", is set with a multitude of rare coloured diamonds.

Gemologists, designers and craftsmen had spent thousands of hours to get the watch right, said the jeweller.

"The Graff Hallucination is a sculptural masterpiece; a celebration of the miracle of coloured diamonds," said company chairman Laurence Graff in a statement.

"For many years I have thought about creating a truly remarkable watch that illustrates our all consuming passion for diamonds. The Hallucination has made my diamond dream a reality."