Home Secretary Theresa May joined police officers of all ranks as they paid tribute to a colleague shot dead as he went to the aid of a member of the public.
Hundreds of people packed St James Church in Clacton-on-Sea to remember Pc Ian Dibell, 41, who was killed near his home.
The memorial service was attended by Pc Dibell's family, chief constables from neighbouring police forces, rank and file officers, and members of the public.
Officers from Essex Police held a guard of honour at the entrance to the church.
Pc Dibell's girlfriend, police community support officer Louise Lilley, his sister-in-law Nicole Dibell, and Essex chief constable Jim Barker-McCardle were delivering tributes during the service.
A message of condolence from the Prince of Wales was read to the congregation.