Ten police officers are taking part in a 110 mile charity walk across Greater Manchester in memory of PCs Nicola Hughes and Fiona Bone, who were shot dead last year.
Officers from the Greater Manchester Police Tameside and Oldham Division are setting off from the Civic Hall at Uppermill.
They will be walking throughout the night for a total of 50 hours before returning to finish at Uppermill on Sunday morning.
Sergeant Stuart Charlesworth of the Tameside West Neighbourhood Policing Team said: "Our walk was originally planned for September with a view of finishing in time for the National Police Memorial Day, but following on from the shootings we made a decision to postpone it to a later date.
"We are now being joined by some of Nicola and Fiona's former colleagues who also want to be able to raise money in their name while doing something worthwhile."
Money raised from the walk will go to the Care of Police Survivors charity.