"Christmas tree" files
20TH-CENTURY FILES KEPT BY THE BBC
Christmas tree files; "Christmas Tree" list; "Christmas tree" list
From the 1930s until the 1980s, the BBC kept a number of clandestine files on applicants accused by the British Security Service (MI5, some of whose agents were stationed within the BBC) of being political subversives, in particular communists or communist sympathisers. These were marked with a distinctive upwards-facing green arrow, which bore resemblance to a Christmas tree and had the effect of blacklisting a number of applicants to BBC roles.