Tim Artus, an instructor at RAF Cranwell, set himself the goal of running the London Marathon with a 40lb backpack.
The aim was to break a world record and raise money for the RAF Benevolent Fund, but in the run up to race Tim suffered an injury that set back his training.
Tim isn't one for quitting, so loaded with his 40-lb pack he set off around the gruelling 26 mile course.
As Tim puts it: "With over £3000 raised for the RAF Benevolent Fund, I felt it was worth the effort to complete the race. I felt relatively ok for the first nine miles, but it was soon after that the wheels started coming off.
"By Tower Bridge I decided it was about survival and so started an enforced run/walk routine to make the finish possible. As such, it was a long second half!"
In the end Tim completed the race in 4 hours 34 seconds, which is inside the old world record, but was beaten on the day by another runner.
Tim said: "No one has broken four hours for running with a 40lb backpack, so maybe there will be a re-run next year! The support in the run up to the race, and on race day was brilliant and I couldn't have asked for more."
Well done Tim!