The Koh-i-Noor, one of the largest cut diamonds in the world, was taken from India by the East India Company during the colonial era and presented to Queen Victoria. It is set in a crown last worn by Charles's grandmother during her coronation.

Pakistan, part of British-ruled India, and Afghanistan have also claimed ownership of it since Indian independence in 1947.

Camilla will wear the Queen Mary crown, commissioned and worn by the consort of King George V for the 1911 coronation. Some changes will be made to it, the palace said, to inset jewels unique to the occasion and to reflect her own style.

"The choice of Queen Mary’s Crown by Her Majesty is the first time in recent history that an existing crown will be used for the Coronation of a Consort instead of a new commission being made, in the interests of sustainability and efficiency," Buckingham Palace said in a statement.

Charles automatically became king of 15 realms, including Canada, New Zealand and Australia, on the death of his mother Queen Elizabeth in September, but his and queen consort Camilla's official coronation will take place on May 6 at London's Westminster Abbey.

The Queen Mary crown will be reset with the Cullinan III, IV and V diamonds, in tribute to the late Queen Elizabeth, the palace said. The diamonds were part of her personal collection and were often worn by her as broaches.

Four of the crown's eight detachable arches will also be removed, the palace said. The crown was taken off display at the Tower of London for the modification work to be carried out.

The last time a queen consort’s crown was re-used was in the 18th century.