Why a flask of tea belongs in your rucksack

There is a particular moment on a long walk when the ground starts to rise, the wind picks up and your hands begin to feel the cold properly. Then you reach the top, or a shoulder of the hill with a view worth stopping for, and you swing the rucksack off your shoulders. If there is a flask inside it, you have just done your future self an enormous favour.

A warm drink tastes better outdoors. That is not sentimentality, it is simple fact. Cold air sharpens the appetite, the effort of the climb makes you grateful for small comforts, and the view does the rest. A mug of tea drunk on a hillside, with your back against a stone wall and nothing to do but look, is one of the great quiet pleasures of slow living. The trick is to prepare it properly, so the drink is still hot and genuinely enjoyable when the moment comes.

Getting the flask ready before you leave

The single biggest mistake people make is pouring tea into a cold flask. A stainless steel vacuum flask will pull heat out of the liquid straight away, and you will be drinking lukewarm tea two hours later. Fix this in two minutes at home.

• Preheat the flask: fill it with boiling water, screw the lid on, and leave it for two to three minutes. Pour that water away and fill immediately with your tea.
• Fill it right to the brim. Air is the enemy of heat. The less empty space at the top, the longer the tea stays hot.
• Choose the right size: a 500ml flask gives two decent mugs, which is about right for two people or one very cold walker.
• Look for a wide mouth. It is far easier to fill, easier to clean and less likely to harbour a stale smell.
• Keep it clean. Rinse after every trip with hot water and a little bicarbonate of soda. Never leave tea sitting in it overnight.

Wrap the filled flask in a fleece, a tea towel or even a thick sock, and bury it in the middle of your rucksack rather than in an outer pocket. That extra layer of insulation makes a surprising difference on a frosty morning.

Brewing tea that survives the journey

Brew it stronger than you would at home. Cold air, exercise and the general business of being outdoors all dull the palate, and a delicate tea will taste of almost nothing on a hilltop. Use an extra bag or a generous spoon of leaves, and let it steep for four or five minutes.

Take the bags or leaves out before the tea goes in the flask. Left in, they keep stewing and turn the brew bitter and tannic. If you take milk, carry it separately in a tiny screw-top bottle and add it to the mug. Milk in the flask itself is not dangerous, but it dulls the flavour and leaves a film that is a nuisance to clean. Black tea with a slice of lemon travels beautifully, as does a spiced brew with cinnamon or a little ginger.

If you want a second flask, make it soup rather than more tea. Nothing beats it on a winter walk, and it turns a brief stop into a proper small meal.

Packing the few things that make the break work

• An enamel mug or the flask's own cup, plus a small cloth to wipe it dry.
• A sit mat or a folded square of foam. Cold, damp ground pulls the warmth out of you fast.
• Gloves you can hold a mug in, or fingerless ones so you can manage the lid.
• A bag for your rubbish and any orange peel, which does not rot as quickly as people assume.
• Something small to eat: flapjack, shortbread, a handful of nuts. Sweet and substantial beats fiddly.

Finding a spot worth stopping in

On an exposed top, the wind will strip the heat from your tea in a minute. Walk twenty or thirty metres down the sheltered side and the difference is remarkable. In Britain the prevailing wind comes from the south-west, so look for the lee side of a dry stone wall, a bank, a gorse bush or a stand of trees facing north-east. A wall that has kept sheep in for two centuries will keep the wind off you too.

Avoid sitting on bare rock if you can; it holds the cold. Dry tussock grass, a flat stone with your mat on top, or a wooden stile all work well. Check for livestock muck before you settle. And step a little way off the path so that other walkers are not obliged to squeeze past you while you sip.

The pause itself

Pour slowly and hold the mug with both hands. Let it cool for a moment rather than gulping it, because the point of this is not the caffeine. Give it twenty minutes at least. Leave the phone in the rucksack. Look at three things close to you, a lichen on the wall, the weave of your glove, then three things a long way off, a ridge, a distant church tower, a line of birds.

Notice what you can hear once your breathing settles. This is slow living in its simplest form: no rush, no queue, nothing to achieve. When the mug is empty, screw the lid back on, repack everything, and take one last look before you shoulder the bag. The walk down will feel lighter for it.