At 07.30 on 1 July 1916, whistles were blown up and down the British front line and thousands of men climbed from their trenches into no man's land - it was the first day of the Battle of the Somme.

To mark this moment 100 years on, Huw Edwards in Thiepval, France, and Kirsty Young in Westminster Abbey, London, present this special live broadcast. The Kings Troop Royal Horse Artillery fire their guns on Parliament Square and two minutes' silence are observed. Show less