Prince Charles has led tributes to police officers who have died in the line of duty including a sergeant who was shot dead two days ago.
The Prince of Wales said Sgt Matiu Ratana's death was the "latest heartbreaking evidence of the risks".
The 54-year-old who died after being shot by a handcuffed suspect was remembered during an online service for National Police Memorial Day.
Prime Minister Boris Johnson said "we own them a huge debt".
The Met commissioner Dame Cressida Dick said the death of a police officer on duty was a "rare thing".
She said her thoughts were with grieving families as six other officers who have died on duty in the past 12 months were also remembered.
Sgt Ratana, from New Zealand, is the eighth police officer in the UK to be shot dead in the past 20 years.
He died in hospital on Friday after a shooting in Croydon Custody Centre. A 23-year-old suspect, who is thought to have shot himself, remains in a critical condition in hospital.
Prince Charles, who made an address ahead of the online service, said: "I particularly wish to remember those officers who have so tragically lost their lives since we met in Glasgow last year.
"The dreadful incident in Croydon on Friday is the latest heartbreaking evidence of the risks faced by our officers daily.
"I would like to send my deepest sympathy to the families of each of these officers who have given their lives."
Reverend Cannon David Wilbraham led the 20-minute service online where a candle was lit to those who had died.
The service which included serving police officers, Prime Minister Boris Johnson would have been held at Lincoln Cathedral before coronavirus restrictions saw it move online.
Mr Johnson said: "The police officers we remember today represent the very best of us. They laid down their lives to prevent us from coming to harm and we own them a huge debt."
Family members, including Lissie Harper wife of PC Andrew Harper also took part in the video that was recorded in advance.
PC Harper, 28, died after he suffered sustained catastrophic injuries when he was dragged behind a getaway car in Berkshire last August.
Reverend Wilbraham said: "In some ways it is all the more poignant for being online.
"The reality of loss must often be felt most in the home."
"It is a sharp focus on the dangers that are faced," he added.
John Apter, of the Police Federation of England and Wales, said: "National Police Memorial Day ensures that police officers who gave their all are never forgotten.
"We must always remember them, their commitment and ultimate sacrifice to public service."
The service is held each year on the nearest Sunday to St Michael's Day, the patron saint of police.
A small service was held at Lincoln Cathedral with Chief Constable Bill Skelly, Reverend Tanya Lord and Phil Clark from the Police Federation, where a candle was lit to those who had died in service.
Dame Cressida had earlier laid a wreath at the National Police Memorial in central London with Mayor of London Sadiq Khan and Home Secretary Priti Patel.
All three stood for a minute's silence to remember officers who had lost their lives while on duty.