The 10in (25cm) high ivory diptych carved with detailed scenes of the Passion of Christ. It took €3.6m (£2.57m) at Sotheby’s in Paris on November 19 and will now form part of the loan exhibition at the Courtauld.

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It is part of the 45 medieval ivories from the Thomson collection being exhibited before they head to the newly-renovated Art Gallery of Ontario in Toronto.

The highly detailed diptych depicting the Passion of Christ was sold by Sotheby's in Paris on November 19 for €3.6m (£2.57). It was bought by London dealer Sam Fogg who was acting for his client, the Thomson collection. It featured on the front page of ATG No 1817, December 1, 2006.

It was one of 27 lots collected by Georges Dormeuil in the early 20th century and was last exhibited in 1913.

Made in Paris in the so-called 'workshop of the Passion diptychs', it measures 10in x 121/2in (25 x 31cm) and appears to be the largest recorded diptych in the group.

On show will also be the Nativity and Last Judgement diptych. Although previously dismissed as a forgery, the ivory recently underwent Carbon-14 dating which proved it was from the 12th or 13th century.

Kenneth Thomson, who died in 2006, began collecting in 1953 during a visit to Bournemouth. He helped fund the transformation of the Art Gallery of Ontario which will have three galleries devoted to the Thomson collection when it reopens.

It will include Rubens' The Massacre of the Innocents, currently on loan to the National Gallery in London, which he bought at Sotheby's in July 2002 for a premium-inclusive £49.5m.