His interest in the wider world was sparked by observing Guinness barges arriving in his native town and speculating about their places of origin.
Having taken his MA in History at UCD, Gallagher joined the Civil Service applying for a position in the Department of External Affairs, as it was then called, starting in the job on 6 January 1969.
Later that year, Aiken was succeeded by Dr Patrick Hillery and then the event took place that was to shape Gallagher's life: the North erupted into violence.
On Saturday, 16 August 1969, Gallagher, as weekend duty officer for the department, encountered a group of nationalist MPs from the North, including Paddy Devlin, who arrived at Iveagh House demanding to meet Taoiseach Jack Lynch to obtain arms for the beleaguered Catholics of the Falls Road in Belfast.
[citation needed] His first foreign posting was to the Irish consulate in San Francisco in August 1971 – he and his college sweetheart, Maeve Farrell, from Ratoath, Co Meath, had just been married the previous month.
His White House contacts proved advantageous when the nascent Irish peace process faced its first major challenge: securing a US visa for Sinn Féin leader Gerry Adams.