Board lumber was cut on site and shipped about 8 km to the rail line.
The German national internees, as distinct from prisoners of war, had largely been classified as "enemy aliens", many shipped from Britain after the fall of France in 1940 under Churchill's "collar the lot" edict.
As most of these were in fact Jewish or political refugees from the Nazi regime (and so would have formally had their German citizenship withdrawn by the authorities there, thus being effectively stateless, even if this factor was not realised or recognised in the UK), after vetting many were allowed to return to Britain to join the armed forces.
Wulff Scherchen was the romantic interest of Benjamin Britten, himself only 26 at the time.
Over 80 years later, with his consent, these heartfelt letters were made into an orchestral song cycle called Serenade for Tenor, Saxophone and Orchestra by composer Lyle Chan.