Then, a visit to the GPO Dollis Hill research centre revealed the problem. The cryostat contained a large number
of transverse, vapour cooled, copper radiation shields, which, on tilting to 45 degrees to receive signals from Telstar
1 near the horizon, resulted in a thermal short circuit of the Scott vapour cooling effect. Replacement with low
thermal conductivity Perspex shields removed the problem, the boil-off dropped rapidly and the UK supply of liquid
helium was suddenly available for everyone again. This success was among the first significant and inspirational
uses of CryoFD.