Leaving school at fifteen, Collins took the British Civil Service examination in Cork in February 1906 and moved to the home of his sister Hannie in London, where he became a boy clerk in the Post Office Savings Bank at Blythe House. In 1910 he became a messenger at a London firm of stockbrokers, Horne and Company. While living in London he studied law at King's College London. He joined the London GAA and, through this, the IRB. Sam Maguire, a republican from Dunmanway, County Cork, introduced the 19-year-old Collins to the IRB. In 1915 he moved to work in the Guaranty Trust Company of New York where he remained until his return to Ireland the following year joining part-time "Craig Gardiner & Co", a firm of accountants in Dawson Street, Dublin.