For a year and a half, Michael studied for the postal exam. At the age of 15, Collins passed and was sent to London to work in a postal savings bank. During this time, he lived with his sister, Johanna, and caught on quickly to the concepts of business and finance. In fact, Collins was so adept with business skills that he was offered a position in America by his brother if he would leave the UK to come to work.
"America's loss was to be Ireland's gain. For if Michael Collins had taken his brother Pat's advice, the Republic of Ireland might not exist today. Watching the storm clouds of World War I gather over Europe, Pat had written to Michael from Chicago urging his younger brother to leave his job in a London financial institution and come to join him in America" (Coogan).
"His eldest brother, John, took over the farm on their father’s death six and a half years later, and Michael continued to live there until he was sixteen, when he took up a job in the Post Office Savings Bank in London. Here he lived at 5 Netherwood Place, Kensington, with his sister Johanna (Hannie), who was also a Post Office employee. Like most Irish people in England they mixed mainly with their compatriots rather than assimilating into English society, and the cultural influences Michael was exposed to were largely Irish. ‘I had Irish friends in London before I arrived,’ he wrote later, ‘and in the intervening years I had made more friends among Irish residents in London. For the most part we lived lives apart. We chose to consider ourselves outposts of our nation.’ This was the classic recipe for a revolutionary nationalist and Collins belonged precisely to the generation of young people most affected by the new forces at work in Irish society. His national school education in Ireland had steeped him in the history of Irish revolutions, ‘old, unhappy, far-off things and battles long ago.’ He shared the enthusiasm for a Gaelic past and the Irish language, which he always found difficult to master, though his parents had been native Irish speakers. A natural athlete, he enjoyed all physical sports, especially football and hurling, and was a very active member of the GAA, becoming secretary of his London club, the Geraldines. The GAA was a recruiting ground for the IRB. Through a Cork friend, Sam Maguire, who also worked in the Post Office in London, Collins was sworn in as an IRB member in 1909, and later was appointed treasurer of the South of England district. This decision determined the entire course of his short life" (A.T.Q. Stewart).
"The schoolboy ambition to be an engineer reasserted itself and this, together with a natural bent for mathematics and an apparent enjoyment in the working of figures, made thoughts of an engineering career in America a distinct possibility. He wrote, ‘Spent the day (Saturday) at the docks. Walked around debating my future. Should it be America?’" (Rex Taylor).
But Pat's suggested arrangement was not to be. Michael was feeling homesick for Ireland. Because of this loneliness, Michael joined the Gaelic League, an organization that encouraged its members to keep the Gaelic language alive and to engage in traditional sports. One group seemed to lead to another and Collins soon joined the Gaelic Athletic Association and next the Irish Republican Brotherhood.
Collins as a young man, strategically placing his hand to cover a small hole in his pants.
Collins was also developing physically and socially. His friends nicknamed him "the Big Fellow" not so much because of his size (he was approximately 5'10" with a stocky build) but because of his tenacity and daredevilry. He was willing to do nearly anything with great enthusiasm and ambition. He grew into a good athlete, a great financier and an incredible politico. Via his IRB connections, Collins heard of a planned insurrection in Dublin. This seemed to fit perfectly with his personal plans; he was hoping to escape conscription for World War I and he had secured a job with an accounting firm in Dublin. Indeed, it appeared the necessary pieces for Collins's career as a revolutionary had fallen into place.