[2] He was imprisoned in Mountjoy Prison in 1922,[3] and was subsequently interned in the Curragh Camp, where he kept an autograph book, collecting signatures including that of Michael Hilliard.
[4] In this capacity, he signed the ultimatum to the British government declaring that, if major concessions were not made immediately, a Sabotage Campaign would be initiated.
[5] On 9 September 1939, he was arrested along with the majority of the IRA Army Council (Matty Tuite, Willy McGuiness, Paedar O'flaherty and Patrick McGrath) at 16 Rathmines Park, Dublin.
This led to a clampdown, including solitary confinement and an incident in which soldiers fired on the inmates, killing one;[7] Grogan was subsequently removed from the camp and given a prison term.
[11] While in gaol, he contested Louth for Sinn Féin at the 1957 Irish general election, taking 9.6% of the first preference votes.