the United Kingdom. In 1986, Powell stated that the Irish National Liberation Army (INLA) had not killed Neave but that "MI6 and their friends" were responsible: Powell cited as his sources information that had been disclosed to him from within the Royal Ulster Constabulary. Margaret Thatcher, however, rejected and dismissed these assertions. In 1985, race riots between the black community and the police broke out in London and in Birmingham, leading Powell to repeat his warning that ethnic civil conflict would be the ultimate outcome of foreign mass migration into the British Isles, and re-issue his call for a government sponsored programme of repatriation. Powell later came into conflict with Thatcher in November 1985 over her support for the Anglo-Irish Agreement. On the day it was signed, 14 November, Powell asked her in the Commons: "Does the Right Hon. Lady understand — if she does not yet understand she soon will — that the penalty for treachery is to fall into public contempt?", the Prime Minister replying that she found his remarks "deeply offensive". Along with other Unionist MPs, Powell resigned his seat in protest and then narrowly regained it at the ensuing by-election. In 1986 the former Irish schoolteacher Seamus Mallon was a new entrant to the House of Commons. During his maiden speech, Mallon quoted the Dutch philosopher Baruch Spinoza, saying "Peace is not an absence of war. It is … a state of mind, a disposition for benevolence, confidence, justice." Powell, sitting close to Mallon, hissed an objection. When Mallon enquired why, Powell said that he had misquoted Spinoza. Mallon stated he had not and, to reconcile the standoff between them, they both proceeded to the library to verify the quote. Mallon was found to have been correct. In 1987, Thatcher visited the Soviet Union, which signified to Powell a "radical transformation which is in progress in both the foreign policy and the defence policy of the United Kingdom". In a speech in the Commons on 7 April, Powell said the nuclear hypothesis had been shaken by two events. The first was the Strategic Defense Initiative or "Star Wars": "Star wars raised the terrible prospect that there might be an effective means of neutralising the inter-continental ballistic missile, whereby the two great giants who held what had become to be seen as the balance of terror would contract out of the game altogether: the deterrent would be