In the 1987 general election a leaflet printed for the Birkenhead candidate before the agent was appointed was "published by the Liberal Agent". That resulted in a Police interview as well - Special Branch I believe.
Helen Michael has had two visits from the police regarding a poster displayed by Barnet traders to highlight the unfairness of the parking charge regime. She’s also been grilled for two hours by two officers from Scotland Yard. It is also clear from the transcript Helen took that a senior Barrister had been engaged to give a legal view on the subject.
The “crime” Helen is alleged to have committed? Not putting an imprint on the posters.