Founded in 1968 in Camden, north London, the Poster Workshop was a hub of radical political art. Inspired by the events of May 1968 in Paris, the Poster Workshop contributed to diverse social movements by creating hand-printed political posters.
A document authored by SDS boss Detective Chief Inspector HN325 Conrad Dixon , reflecting on the first four months of the SDS, reported HN332 Cameron Sinclair being assigned to report on the Poster Workshop.
A printing collective based in Camden, London the Poster Workshop created publicity material for campaigners. The few mentions of the Poster Workshop that appear in Inquiry disclosure feature only in reports on other groups. This suggests that the Poster Workshop was not specifically targeted.
However, the collective did produce posters for many groups that the SDS was spying on, in one example to promote the London School of Economics occupation on October 27 1968.
This is why monitoring the Poster Workshop premises would have been helpful to the SDS although, aside from Dixon stating that Sinclair was monitoring the collective, there is no other evidence that it was a major target for the SDS. See Penetration of Extremist Groups.
Source: The Poster Workshop.