A Hertfordshire policeman will guide Pc David Rathband, the officer blinded by gunman Raoul Moat, in the London Marathon on Sunday.
Pc Gareth Rees, based in Stevenage, broke both legs when he was hit by a car while on duty in December 2008.
Pc Rees, 35, will be accompanying Pc Rathband to raise money for his Blue Lamp Foundation.
The charity raises money for emergency services personnel criminally injured while on duty.
Pc Rees was dealing with an accident on an unlit stretch of the A505 between Baldock and Royston when he was hit by a Vauxhall Corsa travelling between 50 and 55mph.
The driver was later convicted of careless driving.
"I spent a lot of time in hospital after the accident and was told very early on by one of the consultants there that it was very unlikely I would walk again," said Pc Rees.
"That was a shock to hear - I couldn't accept that. I think, in many respects, the consultant did me a favour telling me that because it spurred me on to really get up.
"About four or five months later I took my first steps."
After months of surgery, physiotherapy and rehabilitation, he returned to work in May 2009 and took up an administrative post but has recently returned to the Hertfordshire force's Road Policing Unit.
He said he felt compelled to help when he heard about the injuries sustained by Pc Rathband, who was shot in the face by Raoul Moat in Newcastle in July 2010.
Pc Rees, of Henlow, Bedfordshire, will be leading Pc Rathband on parts of the course using a rein.
The pair will be joined by two friends and hope to complete the race in about eight hours.
"We're not going to be breaking any records by doing the 26 miles. We're getting from A to B to prove we can do it," said Pc Rees.
The Blue Lamp Foundation has raised about £60,000 but hopes the marathon will boost their funds further.
The charity's supporters include millionaire entrepreneur Duncan Bannatyne, from the television programme Dragon's Den.