Full police funeral for Pc Keith Palmer, the officer killed in the Westminster attack
The 48-year-old was stabbed to death by Khalid Masood as he carried out his duties on the cobbled forecourt of the Palace of Westminster.
His coffin will be taken from the Palace of Westminster, where it has lain in rest overnight, to Southwark Cathedral for the funeral today followed by a private cremation.
The Queen gave permission for Pc Palmer's body to rest in Westminster's Chapel of St Mary Undercroft, an honour normally reserved for heads of state.
Full service funerals are normally only held when a police officer or member of staff dies while they are carrying out their duty, Scotland Yard said.
Thousands of officers from across the country are expected to line the streets around the cathedral and could take part in the service as ushers.
Four other innocent people were killed and dozens of others injured in the 82-second atrocity on Wednesday March 22, which ended with Masood being shot dead.
Andreea Cristea, 31, Leslie Rhodes, 75, Kurt Cochran, 54, and Aysha Frade, 44, died after he ploughed into pedestrians on Westminster Bridge.