It is one the toughest things any child has to deal with – waving goodbye to your dad as he goes off to risk his life for Queen and country.

But when RAF Honington airman Cpl Si Simm's three-year-old daughter and 11-month-old son struggled to cope with their beloved father fighting abroad, help was not far away.

Deployed to Iraq, the 30-year-old's long absence meant his two young children took the separation from their dad hard.

So Cpl Simm's wife Sarah contacted Little Troopers, a charity which supports children of parents serving in the British armed forces, to ask for their help.

The organisation was able to help by providing the family with a free 'separation pack', a specially designed resource including postcards and chuff charts, to help ease the pain of being separated.

Mrs Simm and her daughter also benefited from a trip to Disney on Ice, organised by the charity to provide a welcome distraction from the stresses and strains of the deployment.

Cpl Simm, who has served with the Royal Air Force for 11 years and completed several operational tours of duty, was so impressed by the charity's support that he decided he had to give something back.

So after returning from overseas operations in the Middle East in January, Cpl Simm – originally from Ormskirk, West Lancashire – completed his first marathon to raise money for Little Troopers.

Joining thousands of others for the Greater Manchester Marathon on April 7, he finished the 26.2-mile route in 3hrs 57mins – in spite of incurring a hamstring injury at the 14-mile point.

He also smashed his £300 fundraising target, raising £500.

'I have to keep fit and run a lot of miles as part of my role in the RAF but I'd never run a marathon before and it's always been an ambition of mine to complete one,' said Cpl Simm, who has been based at RAF Honington for the entirety of his career.

'Now I've done that, I've definitely got the bug and plan to tackle more in the future.

'I wanted to give something back to this amazing charity, which provided a lifeline for my loved ones when I was serving overseas.

'It can be really tough for the children when I'm away for long periods and the support Little Troopers offers is invaluable.'

Louise Fetigan, founder of Little Troopers, said: 'We are a small charity with big aspirations to support the thousands of children facing unique daily challenges, due to their parent's career choice.

'We were delighted to be able to provide a morale boost to Si's family when he was away on operations.

'To discover that he'd chosen to the support us by running his first ever marathon was really humbling.

'Every penny raised goes towards Little Troopers projects. We are extremely grateful to Si for his efforts.'

You can still donate by visiting https://mydonate.bt.com/fundraisers/simonsimm1