A rare 14th century scientific instrument, found during building work at a Canterbury pub, is to stay in the UK.

The British Museum has raised the £350,000 needed to buy the astrolabe quadrant, discovered in 2005.

Culture Minister Margaret Hodge placed an export ban on the item after it sold at auction in March 2007. It is said to be one of only eight in the world.

Now, after receiving £125,000 from the National Lottery Heritage Fund, £50,000 from the Art Fund and £175,000 from British Museum Friends and other sources, the British Museum has been able to acquire the device, used for telling the time, mapping the stars and making height and depth measurements.

David Barrie, director of The Art Fund, said: “The Canterbury astrolabe quadrant offers an extraordinary insight into the scientific and technological capabilities of Chaucer’s England.“

The quadrant is believed to have been made in 1388 and the British Museum will display it next month.

A spokesman for the museum said astrolabe quadrants were among the most sophisticated calculation tools ever made before the invention of the modern computer.

“This particular example was made for use with the sun with the help of the two sighting vanes attached to one side and a now lost plumb-bob,” she said.

“Besides enabling the user to determine the date of Easter he could use it to determine the times of sunrise and sunset, the time in equal and unequal hours or the geographical latitude - to name but a few of the many functions.”

The brass instrument was found during excavations for an extension to the former House of Agnes hotel at St Dunstan’s.