Kirsty Young introduces live coverage of the centenary commemorations to mark the first day of the Battle of Passchendaele, from Tyne Cot Cemetery in Belgium, to remember the half-a-million casualties sustained during the fighting.Music, readings and veteran testimony are delivered in the cemetery, where almost 12,000 men are buried and 34,000 servicemen are remembered on the memorial to the missing. One hundred years on from the first day of this bloody and horrific First World War battle, the Prince of Wales, the Duke and Duchess of Cambridge, the King and Queen of the Belgians, dignitaries and Belgian and British military are joined by descendants of those who fought, to remember and pay tribute to the bravery and sacrifice of all those who served.Throughout the day, Kirsty is joined by special guests in the studio, including Ian Hislop and Michael Morpurgo, and Dan Snow reports live from the cemetery and talks to some of those taking part.