Shillington had originally planned to join the
Civil Service, however he wanted a more varied career. In 1969, Shillington was appointed Deputy Inspector-General of the RUC, as second-in command to the Inspector-General,
Anthony Peacocke (who, like Shillington, had been educated at Sedbergh and Cambridge). When the
Battle of the Bogside broke out in Derry City in August, Shillington asked for permission to use
CS gas for the first time in the United Kingdom. When that did not halt the rioting, he requested that the
British Army be brought in. Shortly thereafter,
Sir Arthur Young was seconded from the
City of London Police to be the last Inspector-General and the first Chief Constable of the RUC.
James Callaghan, then Home Secretary, sent him to implement the Hunt Report. Young's measures introduced the standard British rank system for police officers in Northern Ireland and disbanded the
Ulster Special Constabulary. Shillington remained as Young's deputy, and when the latter returned to the mainland in 1970 he succeeded him to become the RUC's second Chief Constable. ==Honours and decorations==