Having signed up when he was just 19 years old, Duncan left his home in Muir of Ord to travel down to Bury St Edmunds for basic training at RAF Honington.
He subsequently joined the RAF Regiment, working in Kuwait before the dawn of 9/11 resulted in tours to Iraq and Afghanistan.
He had served for 13 years when he was posted to Afghanistan in 2009 – a tour which changed his life.
Duncan was on routine patrol near Babaji on July 31 that year when an IED exploded under his vehicle, throwing the sergeant more than 30ft in the air and leaving virtually every bone in his body broken.
The only unbroken part was his right arm.
Everyone in the vehicle survived but Duncan took most of the impact.
“We were part of a big operation at that time, Panther’s Claw, when our vehicle hit a roadside IED and was destroyed,” he said.
“The bomb went off right underneath me so I took the shock of the blast.
“Luckily, the other guys with me were okay.
“We got off pretty lightly – we all survived.”
Duncan subsequently spent five months in hospital, four of which he had to lie flat to avoid paralysis. Once doctors had given his spine the all-clear, the focus turned to his legs.
Duncan said: “The doctors didn’t hold out much hope of me walking because my heel bones were completely destroyed.
“I went to Headley Court in Surrey for rehab, just trying to get me to walk.
“I saw a specialist who said I would either have to live with the pain or go for a double amputation.
“I was in constant pain so I decided to get rid of my legs. It was the right decision – I’ve never regretted it.”
Duncan received months of rehabilitation at Headley Court after the amputation on July 1, 2010.
Within weeks he was walking again on his first set of prosthetic limbs.
Duncan’s wife Kim and daughter Lilly, who is now eight, moved from south Wales to a bungalow in Bury to be closer to both him and family. But that came with its own problems.
Duncan said: “The council installed a wet room but it wasn’t well thought out.
“It’s strange having to ask for help when you’ve never had to before – it’s a very difficult thing to do.”
But the RAF Benevolent Fund, which Duncan had made monthly contributions to, was happy to help.
“In the end, they paid for an extension to our house and put a bespoke wet room in for us,” he said.
“It was a gold plated solution and I can’t do enough to thank them.”
He has tried though – raising £12,000 with fellow RAF serviceman Nick Wilson doing a John O’Groats to Land’s End cycle in 2011 in aid of the RAF Benevolent Fund and Help for Heroes.
Duncan (39) now works as a special projects fundraiser for the charity Walking with the Wounded.
Looking back, he has no regrets about his service.
He added: “I wouldn’t change being in the RAF – I feel lucky to be a part of it.
“It’s phenomenal that the 100th anniversary is putting the RAF in the public eye as people either don’t know about it or think it’s all about the Red Arrows.”
Events in Scotland to celebrate RAF’s 100th birthday
2018 marks 100 years of the Royal Air Force (RAF),the world’s first independent air force.
Hundreds of events are being held across the country to celebrate.
One of the many is the Centenary Baton Relay which will see a specially designed baton visit 100 sites associated with the RAF in 100 days.
In Scotland, people will be able to see the baton from May 15 to May 28. The baton will be at RRH Benbecula on May 15, before visiting RRH Saxa Vord on May 22, John O’ Groats on May 23, RAF Tain on May 24, former RAF Kinloss on May 25, former RAF Grangemouth Memorial on May 26, RAF Lossiemouth on May 27 and then ending at the former RAF Leuchars on May 28.
Other events planned for this memorial year include an RAF 100 service at St Giles High Kirk in Edinburgh on June 9. There will be a Big Bang Stem Fair at UHI Perth on June 12; the annual airshow at East Fortune on July 28 and the Royal Edinburgh Military Tattoo will also salute the RAF from August 3 to 25.