1 A person can survive for three weeks without food but for only three days without water. To retain fluids, avoid exertion, don’t smoke, stay in the shade, don’t talk and breathe through the nose. To find water, look in valley bottoms where it naturally drains. Rainwater is drinkable. After going a long time without water, don’t guzzle when you find it. Large gulps will make a dehydrated person vomit, losing even more of the valuable liquid.

2 Most places in the world have vegetation that can be safely eaten. First ensure that a plant is not slimy or worm-eaten. Then crush a small portion. If it smells of bitter almonds or peaches, discard. Rub or squeeze some of the juice on to the skin and if any discomfort, rash or swelling is experienced, discard. Then place on the lips, mouth and tongue, waiting five seconds between each. If there is no irritation swallow a small amount and wait five hours.

3 If you have no idea where you are then the best course is usually to follow waterways downstream. They will clearly define a route and generally lead to populated areas. Before you abandon camp leave signs that you have been there and moved on. Mark the trail as you proceed. Choose a striking feature in the distance and keep heading towards it.

4 Even a shallow depression in the ground will provide some protection from wind. Make a roof to keep the rain off and the warmth in. A few strong branches placed across the hollow can support a light log laid over them, against which shorter boughs and sticks can be stacked to allow water to run off. Laying turf or grass on top can also help.

5 Keep clothing and footwear off the ground — then scorpions, snakes and other nasties are less likely to invade them. Always shake out clothing and check boots before putting them on. Be wary when putting hands in pockets. On waking, take care: centipedes tend to curl for warmth in some of the more private body regions.

Taken from The SAS Survival Handbook by John “Lofty” Wiseman (Collins)