Just because you are paranoid ...
... doesn't mean Special Branch is not following you.
A character shown in a new light at the seminar today was Nancy Cunard, of whom I was vaguely aware as a rebellious socialite. She was, however, I learnt, much more than that, being a writer, scholar and significant political campaigner, as this account indicates. Also here and an image of her by Man Ray here. (The biography by Anne Chisholm is apparently the one to read if you want to know more.)
A scholar studying the recently declassified files told us that while she was often dismissed as being paranoid for complaining about the police following her, in fact they were, very closely. The file only ends with her death in a French hospital in 1965.
Some of the PC Plods must have been seriously out of their depth in the job, however. There was a lovely letter from a local police station reporting the arrival of a letting agent from her flat (called out by neighbours' complaints that "lots of Negros" were going into it). The agent was charmed by her, seems to have accepted her explanation of political work, but immediately rushed down to the police station to hand over the "communist" pamphlets she had given him. A PC was waiting for Special Branch to collect them.