On March 22, Emmy Collett learned she has terminal medullary thyroid cancer, and was given a life expectancy of five years by her doctors.

The news came just six months after Ms Collett reunited with her childhood sweetheart, Jake Coates, whom she has known closely since she was 11 and dated for three years, before separating for university.

Mr Coates, who was living in Australia, flew to the UK and proposed to the former Morden primary school teacher.

Deciding to face their future with optimism, the couple are spending as much time as they can together, and on Sunday set out on a 2,000km tandem bicycle challenge to raise money for The Royal Marsden Cancer Charity, where she is receiving treatment.

Ms Collett said: “It was spur of the moment. We were sitting in the Marsden and decided we wanted to do something together to give back. We thought ‘what better way to all this than with a tandem.’ We thought it would be a great thing to do, a good way to get people interested and keep raising awareness, and something unique.”

Although Ms Collett did not own a bike when she and her fiancé, Mr Coates, decided to do the tandem challenge, she said she has loved training.

Ms Collett said: “I can’t wait. We’re really, really enjoying it!”

They departed from Trafalgar Square, boarded a ferry to Dunkirk, then were set to follow the North Sea Cycle Route to Copenhagen. The route will take them along the North Sea border of France, Belgium, the Netherlands, Germany, and Denmark. The couple plan to arrive in Copenhagen within 18 days.

Ms Collett, a former teacher at Malmesbury Primary School, said: “We decided it would be best to do a reasonably flat route, because even if I was struggling it would be less taxing.”

According to Ms Collett, the couple also chose tandem bikes because Mr Coates could help if she were struggling during the ride. Plus, communication is easier when both are on the same bicycle.

The couple began by training on rented bikes in Battersea Park, but recently purchased their own tandem. They have a small trailer that hooks onto their bike and will contain their tent and other necessities.

Donations can be made on the couple’s JustGiving page, justgiving.com/fundraising/ejtandemonium, and they have already raised more than £60,000 of their £100,000 goal.