[3] His elder brother Sir Richard James Dacres was a field marshal in the British Army and was also awarded the GCB.

[1] Sydney joined the Royal Navy in 1817 at the age of 12, and after serving for ten years, was promoted to lieutenant on 5 May 1827, initially aboard the 46-gun HMS Blonde under Captain Edmund Lyons.

[6] On 18 October Lieutenant Dacres was involved in an attack on the Turkish forces at Morea, during the Greek War of Independence.

He and other lieutenants from Blonde, working in company with French naval forces, landed guns and helped to build batteries.

[8] The St Vincent was at that time the flagship of Rear-Admiral Sir Charles John Napier, commander of the Channel Fleet.

She spent 1853 as part of the Channel squadron, then with the outbreak of the Crimean War Dacres sailed to the Black Sea in 1854 to support operations.

[8] He then became commander in chief of the Channel Squadron on 24 April 1863, a post he held until June 1866 and during which he oversaw the integration of the new ironclads into the fleet.