On a bitter December day last year, while most of us were clinging to a duvet, a group of Cambridgeshire students were settling down in their homemade shelters in the Hertfordshire woodlands, with little more than leaves, plastic sheeting and a sleeping bag. Most did not sleep a wink. And when they were harried by a team of "invaders" at 3am, it seemed like a relief.
But the ordeal wasn't over. They were less than halfway through their 48-hour survival course. How to make a warm, waterproof and camouflaged bivouac was just one of the skills they would learn before the end.
The 22 students are on the National Diploma Public Service course, run by Cambridge Regional College. The three-year course covers modules such as law and society, UK and European politics and history, but students also learn a range of practical skills including first aid, land navigation, outdoor pursuits and sports leadership. Most plan to join the police, fire brigade or armed forces and the course at Cuffley Outdoor Centre is the toughest of the outdoor activities they have done so far.
In the next day or so, they will learn to prepare food, make waterproof shelters, light a fire without matches, trap and snare, collect water, escape and evasion techniques and basic archery.
Course leader Mark Leak, who served in the Royal Air Force Regiment, says:
"We take these guys up to a point where they would normally stop, and we push them that little bit further to show them that the body and mind can take it. The idea is to make them real go-getters, and whatever they want to do in life, they will rise to the challenge and meet it head on."
But this is about more than just getting tough. "Last year, we had a great response," says Mark. "Students' assignment levels and fitness levels shot up. They had a willingness to try new things. It made them more open-minded."
Revived by breakfast, students learn how to make a bivouac. After a night out in their first efforts, the theory is that they will listen closely to the instructors, who help them to improve their shelters for the second night.
They pick up a host of survival skills from chief instructor Joe Hadfield, an ex-paratrooper and former member of the French Foreign Legion. Using sticks and string, they build traps for rabbits and pigs, and light a fire using a tampon and a lock and flint.
These skills, says Joe, are disappearing among a general population cosseted by 24-hour supermarkets and central heating. "The aim of the course is to help students to develop skills so that they can look after the environment, but also live in it," he says. "We're giving back the art of surviving."
Despite the mud and the chill, it is easy to imagine Cuffley in its summer glory. These woods were once inhabited by cattle-grazers. They unwittingly created open spaces under the canopy that make excellent campsites. Cuffley is just 15 minutes from the M25, yet it feels very remote.
The survival course runs only in winter. In summer, it is primary schools that make the most of the scenic 90-acre site. Activities include mountain-biking, archery, assault courses, orienteering and many more.
Students sleep in large tents set up in one of the 12 campsites in the woods, but they have access to full indoor facilities too.
Mark Leak has no doubts about his students' ability to take care of themselves, but says the security of Cuffley is one of its chief assets.
"It's a fantastic place and there are few sites like this," he says.
"Because it's a safe environment, we're confident we can give students an experience they'll never have again."
Cuffley Outdoor Centre, Carbone Hill, Cuffley, Herts EN6 4PR. Telephone 01707 872632; www.thegrid.org.uk email: firstname.lastname@example.org