Pope Francis has given the King a personal gift believed to come from the crucifixion of Christ and that will feature at the coronation.

The pontiff donated shards said to be part of the cross on which Jesus was nailed, known as the True Cross.

The pieces have been included in a special cross that will lead the procession when the King is crowned at London’s Westminster Abbey in May.

The two small shards have been shaped into the centre of the Cross of Wales and encased by a rose crystal gemstone.

The Cross of Wales will be held aloft as it leads the coronation procession at Westminster Abbey on May 6.

“In a significant ecumenical gesture, the Cross of Wales will incorporate a relic of the True Cross, the personal gift of Pope Francis to His Majesty The King to mark the Coronation,” said the Church in Wales, a branch of the Anglican Church, in a statement.

After the coronation, the cross will be shared between the Anglican and Roman Catholic churches in Wales, reports Reuters.

The Cross of Wales is made from recycled silver, Welsh slate and reclaimed wood.

“Its design speaks to our Christian faith, our heritage, our resources and our commitment to sustainability,” said Andrew John, the Anglican Archbishop of Wales.

“We are delighted too that its first use will be to guide their majesties into Westminster Abbey at the Coronation Service.”

The first rehearsal for the King’s coronation took place this week as the military paraded through the quiet streets of central London.

Hundreds of military personnel followed the route on horseback.

The coronation procession stretches to just 2.1 kilometres – about a quarter of the length of the late Queen’s eight-kilometre celebratory journey, which went through Piccadilly, Oxford Street and Regent Street.

A policeman guides a procession rehearsal along the Mall in central London. Photo: Getty

The grand procession in 1953 took two hours and featured tens of thousands of participants, with the four-kilometre cavalcade taking 45 minutes to pass any given point.

The King and Queen Consort will be taken to Westminster Abbey in the Diamond Jubilee State Coach and return via the same route in the Gold State Coach.

The coronation will feature the largest military ceremonial operation in 70 years, with more than 6000 men and women of the UK’s armed forces taking part.

Sailors, soldiers and aviators from across Britain and the breadth of the Commonwealth will accompany the monarch and his wife to and from Westminster Abbey

Almost 400 armed forces personnel from at least 35 Commonwealth countries will also be on parade to mark the historic moment.