After being removed from the Labour Party and SLL that year, Cadogan became an editor for a Trotskyist magazine called International Socialism in 1960.
He took the controversial decision, purportedly on the grounds of freedom of speech, to permit both the Paedophile Information Exchange and National Front (NF) to meet at the society's premises.
Following opposition to the NF in Red Lion Square, which had resulted in violent disorder and the death of Kevin Gately, the Anarchist Black Cross criticised the South Place Ethical Society’s superannuated mode of governance, which had given Cadogan unchecked control of Conway Hall, while accusing Cadogan himself of being a police informant, of broader collaboration with the NF, and of being a charlatan who had obtained his position for financial gain rather than a commitment to humanism.
[6] During Lord Scarman’s inquiry into the events leading to Gately’s death Cadogan blamed Liberation and the International Marxist Group for the disorder, whilst praising the violent police conduct toward anti-fascist protestors.
Following the Battle of Red Lion Square Cadogan forced trustees of the South Place Ethical Society to agree to continue hosting the NF at Conway Hall, only later passing on information about the far-right group to the Attorney General.