The Welshman joined the team in 2011 and made an instant impact with his performances, culminating with a Paralympic gold medal in the individual pursuit at London 2012, along with a pair of silver medals in the kilo on the track and the time-trial on the road.

Just months before his success at the Paralympics, Colbourne notched up a world title in the C1 three kilometres individual pursuit at the 2012 International Cycling Union (UCI) Para-Cycling Track World Championships in Los Angeles.

He played volleyball at a national level before a paragliding accident in May 2009 resulted in a broken back, which required five months of intense physiotherapy before he was able to walk again.

After regaining his ability to walk, he set himself the goal of competing in his first Para-cycling event in 2010, where he won two gold medals at the Wales Grand Prix in Newport, before making his way into the Britain squad a year later.

"My decision to retire was prompted by my age and by being honest with myself," said Colbourne.

"I don't feel I have the physical capabilities to continue for the next three years to Rio.

"I've really enjoyed my Para-cycling career, the standout highlight being winning gold at the Paralympic Games in London 2012."

Mark Colbourne won a gold and two silver medals at the London 2012 Paralympic Games just two years after taking up the sport

Colbourne also spoke of his plans for the future following his retirement.

"I'm looking forward to being more involved with my Paralympic Ambassador role for the London Velodrome - I'm very proud of that," he said.

"I'm going to be setting up my own cycling training camp company which will help other people to learn and develop their cycling skills from grass-roots up to club level.

"I'm also going to continue with my professional speaking with the aim of sharing my story and helping other people to change and improve their lives."

British Cycling's Para-cycling performance manager Gareth Sheppard paid tribute to Colbourne and the impact he had on his team-mates in the short time he spent on the British squad.

"It's been a pleasure to work with Mark and he's been a real asset to the team," he said.

"His Para-cycling career has been short but successful and I know he's been a real inspiration to both his team-mates and also to impaired cyclists in general.

"On behalf of everyone in the GB Cycling Team, I'd like to wish Mark the best of luck for the future."

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