The SNP is to demand the return to Scotland of a priceless collection of 12th-century chess pieces held by the British Museum in London.

The nationalists will make the “repatriation” of the Lewis chessmen a key plank of its forthcoming general election campaign.

Alex Salmond, the SNP leader, is due to table an early day motion at Westminster this week to put pressure on the museum to return the figures to the Western Isles, where they were unearthed in 1831.

The pieces, crafted from walrus ivory and whales’ teeth, are regarded as one of the British Museum’s greatest archeological treasures.

Replicas of the collection, comprising forlorn bishops, brooding queens and soldiers biting the edges of their shields in terror or rage, featured in Harry Potter and the Philosopher’s Stone, the film of the book by JK Rowling.

The pieces are thought to belong to at least four different sets found on Uig on the northern most island of the Hebrides in about 1831 when they were exhibited at the Society of Antiquaries in Scotland.

They are believed to have been hidden in a sand dune placed in a small, drystone chamber. An inquisitive islander is thought to have broken into the chamber and discovered the collection after the sea eroded the sandbank, exposing the cache.

Of the 93 chessmen, 11 are in Edinburgh’s National Museum of Scotland and 82 are in the British Museum.

Salmond’s motion states that the chessmen are rarely seen on Lewis and calls for ownership of the collection to pass to the people of the Western Isles, where they should be put on permanent display.

“It is high time the issue of the Lewis chessmen was resolved. These important artefacts should be back where they were found, housed and looked after by the people of Lewis.

“It is not good enough that they are occasionally loaned back to the Western Isles. This position should be reversed and the chessmen brought home. The islanders should then decide who to loan them to, including, I hope, to Scotland’s national museum and museums elsewhere.”

A spokeswoman for the British Museum said: “We are a world museum housing objects from all cultures from across the globe. We are committed to providing access to this collection to the widest possible public, to the 5m visitors the museum gets per year and, through an extensive loan programme, to the broader world.”

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