Now more than four fifths of the way to completing his extraordinary challenge and equalling Barclay's 200- year-old effort Dunwoody has entered the penultimate week of walking.

Tests carried out by students from the University of Ulster, who are monitoring his physiological performance, show that he is using about 5000 calories a day – twice as much as normal.

Aiming to finish the challenge on Darley July Cup Day on Friday, Dunwoody, will have walked one mile each hour continuously for a thousand hours.

Having already been joined by a host of celebrities, including Bond Girl Rachel Grant, novelist Jilly Cooper and Champion National Hunt jockey Tony McCoy, Thursday saw Dunwoody joined by Newmarket police officer Nik Chapman, who once worked in racing and whose family is still involved in the sport. Pc Chapman made the walk part of his beat.

"I spend much of my time out on patrol in Newmarket town centre, so I thought why not use that patrol to join the walk and raise more money?" he said.

On Friday, representatives from the Alzheimer's Society, together with Newmarket trainer Micky Quinn and Olympic badminton silver medalist Gail Emms, joined in the Memory Walk.

Dunwoody's father suffers from Alzheimer's and the Alzheimer's Society is one of the charities that will benefit from his historic effort the others being Sparks, the children's research charity, Spinal Research and Racing Welfare.

On Saturday, it was the turn of jockey Eddie Ahern and former Norwich City, West Ham United and Newcastle United manager Glenn Roeder who joined Dunwoody's sister Gail, her husband Paul and their children, George and Lily.

On Monday, current champion jockey Ryan Moore and Foyle's War actress Honeysuckle Weeks, also clocked up some miles

"It's been a tough but exhilarating challenge so far," Dunwoody said.

Stars still expected to take part in the Bury Road-based challenge include former Scottish rugby star Kenny Logan and his BBC TV presenter wife Gabby, cricketing legend Michael 'Whispering Death' Holding and Channel 4 Racing's John McCririck.

Yesterday, it was the turn of Newmarket's favourite Italian Frankie Dettori.

On Sunday July 12, two days after Dunwoody is set to finish his epic challenge, the public are being invited to join the Newmarket Trainers to walk four and a half miles over the historic Newmarket Town Plate course starting at 11am.

Anyone who would like to take part should contact Ron Wallwork on 01638 751 869, or e-mail randjwallwork@ btinternet.com.

Dunwoody will start the walk and among the trainers who have signed up so far are Sir Michael Stoute, Chris Wall and Mark Tompkins.

Entry fees are six guineas (£6.30).