Soldiers and civilians will be running side-by-side in a gruelling 10-mile charity challenge in Colchester later.
The event can be completed as a cross-country run in trainers or as the P Company Challenge, wearing boots and carrying a 35lb rucksack - known as "tabbing".
With a target to finish within 1hr 50mins, the challenge replicates one of the key fitness tests for the Parachute Regiment and Airborne Forces.
Profits from entrance fees raise money for The Parachute Regiment Charity, which supports Paras and their families who are in need, but runners are free to collect sponsorship for any charity.
The Paras' 10 has been run at Catterick, where Para recruits train, since 2008 and runners have so far raised £1m for a wide range of charities.
The Red Devils, The Parachute Regiment's display team, will descend on Abbeyfield just before the race, then a 105mm Light Gun fire and a fanfare sounded by The Band of The Parachute Regiment will start off both tabbers and runners at 11:00.
The route will take runners through Merville Barracks and Friday Woods, using the same hills and water obstacles crossed by soldiers on training runs.
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