Richard Dunwoody has completed his biggest challenge to date – walking 2,000 miles across Japan.

The two-time Grand National winner hiked the length of the country’s three largest islands in 100 days, raising over £14,000 for Sarcoma UK.

Richard said he was “delighted and relieved” to have completed the trek.

“It has been an incredible and, at times, gruelling experience,” he said. “It has also been a humbling experience and I will never forget the kindness and generosity of the Japanese as I have travelled through their country.”

Richard wanted to raise money for and awareness of the bone and soft tissue cancer charity, as his 21-year-old nephew George is suffering with the condition and has undergone chemotherapy and proton therapy.

“I was made aware of Sarcoma UK as a result and wanted to do something positive to help promote the fantastic work and ground-breaking research they do,” said Richard before he started the challenge.

Since he retired in 1999, Richard has reached both the north and south poles, raising more than £250,000 for charity. But this most recent challenge was his longest yet.

“The hike has been mentally and physically tough at times, but it has been nothing to what George has had to endure during the past 20 months,” Richard said.

“He certainly has been a huge inspiration when things became a touch difficult during the past three months and I hope and pray that in the very near future he can make a full recovery from this terrible disease.”

Richard thanked Diana Cooper, Yasuko Sawai, Milky Kora,Yasuhiro Kihara, Toshiyuki Kamimura and his family and “all those who came and walked some miles along the way or who turned up to offer encouragement sometimes in the most remote places”.

He added: “A big thanks to Cheveley Park Stud, for their generosity from the outset, and Richard Callaway and Nike for their supply of Pegasus trainers (of which I have needed several pairs!).

“I’d also like to say a huge thank you to those of you who have already donated to the charity as every penny is truly appreciated, and I hope in the coming weeks that we can reach our target.

“Finally, a very special thank you to my girlfriend Olivia who not only has helped plan and set this challenge in motion but has had the not-so-easy job of looking after our one-year-old daughter, Milly, while I have been away.”