From the 1930s until the 1980s, the BBC kept a number of clandestine files on applicants accused by MI5 of political subversion, in particular those deemed to be communists or fellow travellers of communism. 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. Knowledge of these files was made public in 1985 after being reported on by The Observer; by this time, the practice had ceased, but a number of files remained. These were destroyed in the 1990s following the end of the Cold War.