He is also remembered in the political sphere for recruiting the nationalist leader Michael Collins to the Irish Republican Brotherhood in 1909 and for many years was one of Collins right hand men. As Collins's chief intelligence officer in London, Maguire became the centre of Scotland Yard's investigation into the assassination of Sir Henry Wilson. Maguire was tipped off and fled to Dublin in December 1923 where he got a job in the newly established Irish civil service. Because of his political opinions and his sympathies to the Anti-Treaty forces, he quickly clashed with his superiors and was dismissed.