A couple from Berkshire are setting off on a bike ride to China and back.
The trip has been financed by the couple's redundancy money
Richard Mason, 35, and Kat Wilkinson, 28, decided to take up the challenge, in aid of Cancer Research UK, after Ms Wilkinson lost her mother to lymphoma.
The couple, who were recently made redundant from work, are leaving their home in Caversham on Monday.
The 20,000-mile (32,187km) journey will take them through 27 countries in about 18 months and, if all goes well, they will return by Christmas 2007.
Mr Mason told the BBC News website that their trip could take longer.
He said: "If we find a country that we like, we might spend a bit more time there."
Ms Wilkinson's mother Yvonne was diagnosed with cancer in October, 2003 and died on her daughter's 26th birthday, in January 2004.
She said the trip is giving her a chance to do something that would make her mother proud.
Mr Mason said they were hoping to be granted visas so that they can go through Iran.
"We're waiting to apply until we get to Istanbul because otherwise they will run out before we get there," he said.
He added: "We are not too worried about it. We've been checking the Foreign Office website regularly. It should be OK as long as we get the visas."
The former civil servants have financed their trip from their redundancy money and hope to raise more than £5,000 for the charity.
The first leg of the journey will take them to Dover, from where they will cross over to France on Thursday.
They will then travel through Europe, Turkey, Iran, India and several far eastern countries, including Cambodia and Vietnam, en route to China.
Their return trip will take them through Japan, South Korea, Kazakhstan and Russia before returning to Europe.