After the First World War the nation's timber stocks were at their lowest level with many trees being taken for the trenches and also used for coffins. 2019 marks the centenary of the Forestry Commission which helped create new woodlands to replenish stocks. Among them was Thetford Forest in Norfolk. Writer Ian Marchant explores how it was created and what it looks like now. Things don't stand still though and some of the original species are being replaced with others that can weather climate change. The people and animals aren't standing still either. Although they weren't originally encouraged to use the forest today visitors are crucial. Ian gets up early to join the cani-cross club - human runners who attach themselves to dogs to race as a team - and the alpaca walkers.