Richard Graves MacDonnell
Brinkley went to Royal School Dungannon before entering Trinity College, where he received the highest records in mathematics and classics. After graduating he chose upon a military career and was subsequently accepted at the Royal Military Academy, Woolwich, becoming an artillery officer. In this capacity his cousin, Sir Richard Graves MacDonnell the 6th Governor of Hong Kong (1866–1872), invited him out to the east to serve as his Aide-de-camp and Adjutant.