Winter wild camping in the UK hills gives you the sort of night you remember for years: a still, starry sky, frost forming on the guylines, and the whole ridge to yourself. It also tests your kit in a way summer never does. The cold isn't usually the problem — damp is. A down bag that has taken on a little moisture loses loft fast, and a wet synthetic bag will never give you back the warmth it advertised. Most of the work is done before you get in the bag: pack smart, separate your layers, and manage the water you and the weather put into the tent.

Why Winter Damp Catches People Out

Cold air holds far less moisture than warm air, so the water vapour that has been happily invisible all evening turns into liquid the moment it meets something cold — a tent wall, a metal zip, the outer of your sleeping bag. Meanwhile you are producing water vapour yourself: every breath adds moisture to the air inside the tent, and over a night that adds up to the best part of half a litre per person. Damp clothing and boots add more.

That matters because insulation works on trapped air. Once fibres or down clusters clump together with moisture, the loft collapses and the warmth you planned for disappears. On a one-night trip you might get away with it. On a three-day bothy-and-ridge wander, damp kit turns into a genuine safety issue.

Pack Your Layers Separately

The single best habit is to treat your rucksack like a set of independent waterproof compartments rather than one big bag. A rucksack liner helps, but liners leak at the seams and everything inside still shares the same damp air.

• Sleeping bag: its own roll-top dry bag, 20–30 litres, squeezed rather than crushed. Nothing sharp, nothing wet, nothing else in with it.
• Spare baselayer and socks: one small dry bag, kept sealed all day as your "emergency dry" layer.
• Insulating midlayer or down jacket: its own bag. This is the layer you want dry at the summit and drier still at camp.
• Waterproof shell and overtrousers: separate bag or outer pocket. They are wet and dirty by definition, so never let them share with down.
• Gloves, hat, buff: a small bag each, or one bag you never open with wet hands.
• Food, stove, electronics: keep them apart from clothing so a leaking fuel bottle or a burst porridge sachet cannot ruin your insulation.

Roll the top three times and squeeze the air out before you close it. A dry bag that is half full of air and closed loosely will pump damp air in and out all day as you walk.

Decide What Comes Into the Tent

Before you pitch, make a decision about the porch. Wet boots, wet overtrousers and a sodden pack cover should stay outside or in the porch area, ideally inside a sacrificial bag so they don't soak everything else. If you must bring boots in — and in serious weather you should, so they don't freeze solid — bag them and keep them at the far end, away from your sleeping mat.

Bring in only what you want to dry or keep warm: socks, gloves, hat, the baselayer you slept in. A small microfibre cloth is worth its weight for wiping the inside of the tent walls before you settle, and again in the morning. Wring it out outside, not into the porch.

Win the Condensation Battle

Condensation is not a sign of a bad tent; it is a sign of a sealed one. Your job is to move moist air out before it settles on cold fabric.

• Pitch for airflow. Avoid hollows and sheltered dips where cold, damp air pools. A breezy shoulder of hillside is warmer and drier than a still, grassy hollow.
• Open the vents, and leave the inner door ajar. Slightly counter-intuitive on a frosty night, but a trickle of air through the tent is what keeps the walls from streaming.
• Cook outside or in the porch whenever conditions allow, and never cook in a closed inner tent — the steam is only half the problem; the other half is carbon monoxide.
• Keep the bag off the walls. A sleeping bag touching cold flysheet will wick water all night long.
• Wipe down before sleeping and first thing in the morning, when condensation is heaviest and before it drips onto your insulation.

If you regularly camp in damp British conditions, a breathable bivvy bag or a lightweight liner inside your sleeping bag adds a useful extra barrier and keeps drips off the shell fabric.

Overnight Tricks That Protect Your Insulation

Fill a wide-mouthed water bottle with hot water, wrap it in a sock so it isn't too hot against skin, and put it in the foot of your sleeping bag. It warms the bag, and the gentle warmth drives a little moisture out through the fabric overnight. Damp socks placed in the bag's foot will dry a bit, but be honest about the trade-off: the moisture has to go somewhere, and often it goes into your down. On a short trip, dry small items next to your torso in a sealed bag and accept the compromise. On longer trips, keep damp items bagged and separate, and dry them properly when you get a sunny, breezy lunch stop.

Don't sleep in your down jacket — the loft compresses under you and it soaks up sweat. Use it as a pillow, or drape it over the top of the bag if you're cold. In the morning, shake the bag out, turn it inside out if you can, and give it ten minutes of sun and breeze while you eat breakfast.

Repack the Same Way Every Morning

Do the same sequence every day until it is automatic: bag the damp items, seal the dry ones, check the inside of the rucksack for cold, clammy patches that mean a leak, and repack the sleeping bag first so it goes into a dry bag while your hands are still dry. Carry one spare carrier bag flattened in a pocket for surprises. Do that, and a winter night on the hills becomes a genuinely comfortable thing — which is usually what makes you want to go back out the following weekend.