Zay Harding travels in winter to the far north of Siberia, deep inside the Arctic Circle, on the world’s most northerly railway lines. Having to contend with average temperatures around minus 20 degrees Centigrade, and frequent heavy snowfall, Siberia’s Ice Trains are the toughest of tough trains.

Starting his journey in the historic former capital of Siberia, Tobolski, Zay travels around 1000 miles north of the well-known Trans-Siberian Railway to Russia’s largest natural gas field at Novy Urengoy, on the edge of the Arctic Circle.

From Novy Urengoy, Zay sees a new cross-Arctic railway line under construction. Remarkably, it will follow the route of an abandoned train line – the so-called ‘Railway of Death’ – built before the discovery of gas, during Soviet times, by prisoners of Stalin’s forced labour camps, the infamous gulag.

Along the way, they visit a sombre reminder of what took place here back in the days of the Communist gulag – one of the 150 or so Stalin-era labour camps which, overall, at the height of railway construction in the early 1950s, housed an estimated 80,000 prisoners, many of whom were political dissidents.