Richard Graves MacDonnell
Mercer rose through the administration, becoming Colonial Treasurer (1845–1854), Auditor General (1854–1858), Colonial Secretary (1854–1868), and, ultimately, Administrator, during a hiatus between Governors from 15 March 1865 to 11 March 1866. He was succeeded by Sir Richard Graves MacDonnell, who became the 6th Governor of Hong Kong.