This FDC was issued for the first of the Royal Mail millennium stamp series. The 'Inventors' stamp issue featured Alan Turing's head as the 'father' of modern computer science. So we set out to feature the Colossus computer installed at Bletchley Park in 1943. This was the world's first programmable electronic computer and the fact was kept secret for another 30 years.
We thought the design was a disaster and full of errors including the spelling of 'Colossus' in the cancel. So we only issued 200. But collectors loved and it sold out quickly. Unlikely anyone will part with one for less than £150.