At NATO’s SHAPE military headquarters near Mons in Belgium - a daily endurance test begins.
British personnel and one Dutch marine are aiming to complete seven marathons in seven days.
The decision was to cover 26.2 miles a day for a week.
Money raised would go to British and Dutch cancer research and support charities.
The dedicated group of runners is looked after by equally dedicated supporters.
The extreme nature of seven marathons in seven days means that stops are permitted.
If you'd like to donate to the cause click here: http://uk.virginmoneygiving.com/team/ShapeSeven