Which conspiracy theories have been proved true? Anne Gibson, Leicester Send new questions to nq@theguardian.com. Readers reply True? That’s what they want you to think. sparklesthewonderhen The 1980s theory that there were moves afoot to institute a culture of mass surveillance in the UK, with a system of cameras watching everybody in public spaces. Of course, nobody would ever stand for that … ElCommentario It’s funny that some people claim that climate change is a conspiracy when there was an actual conspiracy by the organisations that wanted to cover it up. I mean, who is most likely to have the resources and motivation for something like this? University researchers or the richest companies on the planet? JohnI Well, the one about the establishment conspiring to stop Brexit is clearly nonsense. Deeply disappointing, really: the one time you really need a deep-state conspiracy to work, it turns out it wasn’t a thing. Brutha Easy to forget now, but for a long time – far too long, in fact – it was thought that accusations of police negligence at Hillsborough were of little substance and that it was just football hooligans trying to deflect from their own misbehaviour. It took far too long for the truth to come out, but thank God it did. garythenotrashcougar I think nationalists in Northern Ireland long suspected collusion between crown forces and loyalist terrorists in murders of nationalists; that has now been demonstrated. A conspiracy theory about a conspiracy that wasn’t theoretical. Sorry if that darkens the mood. Sayingmypeace I once saw a bumper sticker that read: “Just because I’m paranoid it doesn’t mean they’re not following me.” Kevin Monahan For decades, rumours circulated that the US government secretly performed medical experiments on black men. In 1972, it was eventually revealed that, since 1932, the publicly funded “Tuskegee experiment” had deliberately failed to treat syphilis in more than 600 African American men in order to study the long-term effects of the disease. The men were instead given disguised placebos – even after penicillin had become the standard treatment – and occasionally endured cruel procedures. In 1974, a multimillion-dollar class-action lawsuit was settled out of court (including lifetime health benefits) with the surviving participants. Also, the long running conspiracy theory that the US ran a “psyops” programme between the 1950s and early 1970s based on Nazi groundwork (and some imported personnel) was eventually found to be true – there really was a programme called Project MKUltra. MKUltra subjected US and Canadian citizens – through colleges, universities, hospitals, prisons and pharmaceutical companies – to the covert, nonconsensual administration of high doses of LSD, hypnosis, electroshocks, isolation, sensory deprivation and verbal and sexual abuse to explore weakening people and forcing confessions through brainwashing and psychological torture. In 1973, the director of the CIA, Richard Helms, ordered that all documents related to MKUltra be destroyed. However, a cache documents was discovered following a freedom of information request in 1977, which led to Senate hearings. MKUltra was declassified in 2001. HaveYouFedTheFish