Relatives of police officers who have died will light candles and offer prayers in their honour at an annual memorial service.
Around 2,000 family members, friends and dignitaries are expected to gather at St Paul's Cathedral in London this afternoon.
The Prince of Wales, who is patron, will join Home Secretary Amber Rudd and other guests in remembering fallen officers at the 13th National Police Memorial Day.
Among those to be specially honoured is Pc Dave Phillips who was knocked down and killed by a teenage car thief in October last year.
His eight-year-old daughter Abigail will light a candle to remember the father-of-two who was killed as he set down a tyre-puncturing stinger device in a bid to stop a stolen Mitsubishi vehicle during a police pursuit in Wallasey, Merseyside.
The relatives of other officers killed in the line of duty will represent Wales, Scotland and Northern Ireland as they too light candles, while prayers will be offered by family members including Paul Bone, father of Constable Fiona Bone, who was murdered by one-eyed gangster Dale Cregan four years ago.
Inspector Joe Holness, QPM, founder of National Police Memorial Day, said: "This is a proud day that means so much to the families and friends who have lost loved ones in the line of duty.
"National Police Memorial Day unites the country in national recognition of officers who have given us their all. It is a significant day of remembrance to ensure our fallen officers must not, and will not, be forgotten."