After the 2018 Douma chemical attack in which the Syrian government used chemical weapons on Syrian citizens, the SPM developed a conspiracy theory that the attack had been staged by the White Helmets civil defence organisation. The SPM published a paper, co-authored by McKeigue, in which a number of alternative theories about the attack in Douma were outlined. One SPM theory was that the White Helmets organisation had constructed gas chambers to kill citizens as part of an elaborate false flag scheme to lay blame for the deaths on the Syrian government. The false flag conspiracy theory was not original; rather, McKeigue had, “borrowed the gas chamber idea from a retired American pharmacologist, Denis O'Brien, who described in a self-published paper how it had come to him in a dream after he had eaten an anchovy pizza”.