Today we give ourselves a serious scare. Our plan is to climb the pyramidal peak behind our camp, trek diagonally to the edge of the ridge, then follow the deer track we are sure to find there to the top. Simple. So simple that we take no map, no axe to mark a trail and no GPS navigation system.

We satisfy our British need to reach the summit in about two hours. We are in thick forest the whole way, with no view. Coming down, the terrain gets in the way.

Under the trees, the ridge which had appeared so triangular has many sub-ridges. We follow the wrong one, as we discover when we come to a landslide.

This is when panic sets in. We are in Siberia, not the Lake District. There are tigers, and bears - we have found plenty of their tracks (and dung) on the way up. There are forested mountains in all directions, all looking very alike.

There are two possibilities. One: head downhill to the valley we can see, find a stream and follow it - hopefully to our river, the Armu. (But what if we have inadvertently crossed the watershed?). Option two: cross the ridge and find a view in the opposite direction. Maybe this will make us feel better, at least.

Option two seems best, so we duly clamber back up and around. We take stock of our gear and food: one-and-a-half bars of chocolate, a litre of water, one Swiss Army knife, a cigarette lighter, and two compasses between three of us. We also have a nearly-full bottle of insect repellent. There are eight hours of daylight left. We consider the possibility of spending the night in the forest.

The view from the other side of the ridge is more encouraging, however; that large river has to be the Armu. But there is an island. We did not pass an island in the canoe the previous day, so this must be downstream of our camp.

We start the steep descent, deviating northwards so that we will arrive further upstream. Two hours later, we reach a river. The bad news is that it’s not the Armu.

It is far too small. There is only one realistic option now: follow it downstream. If we’re lucky, it will be a tributary of the Armu. We should arrive somewhere far downstream of our camp, then start the laborious trek up the river’s edge. We slosh through the shallows, moving purposefully, not talking now. I think everyone is quite worried.

Some time later we find footprints, then a cigarette packet (not too badly rotted), and finally a towel - my own towel, which I’d left to dry on a rock when we set off. Somehow, against our most hopeful estimates of our location, in six hours on the mountainside we have achieved that most British of traditions: a circular walk.

Simon Chapman is head of physics at Morecambe high school, Lancashire.

Follow his expedition to Siberia every week in The TES this summer. He is videoconferencing with summer schools in Knowsley at www.kirkbyclc.org.ukexplorers