On Sunday , 21 November 1920 , the Headquarters Intelligence Staff of the IRA and its special Counterintelligence Branch under the leadership of Michael Collins assassinated 14 of Cumming 's case officers . Many agents appear to have escaped the IRA execution squads that morning , but Whitehall feared that more of its professional agents would be identified and suffer the same fate ; this prompted the hasty withdrawal of most of the remaining SIS agents from Ireland in the days that followed . A blue plaque was unveiled on 30 March 2015 in Cumming 's name at the SIS headquarters at 2 Whitehall Court
assassinated 14
Bloody Sunday (1920)
Mansfield Smith-Cumming