After taking a job in the British Civil Service in London, Maguire joined and captained the successful London Hibernians Gaelic Football team to several All-Ireland finals between 1900 and 1904.
In 1907 Sam went into the administration of the London GAA, becoming the Chairman of the London County Board and a regular delegate to the Annual Congress of the GAA He finally became a trustee of Croke Park. Coincidentally, Vice-Chairman of the London County Board was Liam McCarthy born in London in 1851 of a Cork father and a Limerick mother, who also worked in the London Post Office. Liam McCarthy's name is commemorated on. the All-Ireland Senior Hurling Championship Cup.
The cup was designed and presented to the GAA in his honour after his death at the age of 48 from consumption.
He is also remembered in the political sphere for recruiting the nationalist leader Michael Collins to the Irish Republican Brotherhood.