The Orange-based officer completed an excruciating 24 laps of the racetrack - totalling just over 149 kilometres - in a little over a 24-hour period.

Mr Mounce-Stephens, stationed at Orange Police Station, has been raising money and awareness for NSW Police Legacy.

As part of his campaign, he undertook the 24-hour effort at the iconic Mount, starting at 9am Saturday and running and walking around the circuit for a full day.

His partner Pip Press, who parked herself at 'base camp' opposite Rydges Hotel at the bottom of Conrod Straight, said Mr Mounce-Stephens had held up well given the gruelling task.

"He ran the first six laps, and by 4pm was onto the ninth [lap]," Ms Press said, adding that he hadn't had to walk a lap on his own because of an army of supporters by his side.

"People have been amazing," she said.

At 7.40am on Sunday, when Mr Mounce-Stephens had just completed his 22^nd lap, the enormous effort was clearly taking its toll.

"I'm in so much pain, coming down the hill is agonising on my legs," he said.

He paid tribute to everyone who had come and walked alongside him, saying he didn't think he would have been able to keep going without their support.

"Honestly, they have kept me going," Mr Mounce-Stephens said of his fellow walkers.

They were especially helpful in the dead of night, and as the tally of laps began to climb.

At 12.20am on Sunday Mr Mounce-Stephens had a group of 13 walkers alongside him. Hours later, as he attempted his third last lap, that number had grown to over 20.

"I"d just like to say thanks to everyone for being here for me,' he said.

"There's no way I could have finished otherwise. The people who did it with me carried me through."

He also thanked Ms Press - "she has been amazing" - who stayed at base camp for the entire event.

As for his post-walk plans? Simple - have something to eat, and go straight to sleep.

Anyone wanting to donate to Police Legacy can do so at www.lapsforlegacy.gofundraise.com.au.