1. Sinclair Alexander-Sinclair was born in Malta, the second son of Captain John Hobhouse Inglis Alexander of the Royal Navy, who served as aide-de-camp to Queen Victoria, and Isabella Barbara Hume, daughter of Thomas Cochrane Hume.

1. Sinclair Alexander-Sinclair was born in Malta, the second son of Captain John Hobhouse Inglis Alexander of the Royal Navy, who served as aide-de-camp to Queen Victoria, and Isabella Barbara Hume, daughter of Thomas Cochrane Hume.
Edwyn Alexander-Sinclair succeeded his elder brother in the Southbar property in 1892 and two years later adopted the additional name of Sinclair on succeeding to the estate of Freswick in Caithness.
Edwyn Sinclair Alexander-Sinclair was first educated at Twyford School He was made lieutenant in 1890, and served as flag-lieutenant to both Admiral Tracey and Admiral Sir Michael Culme-Seymour, gaining promotion to commander in January 1901.
Edwyn Alexander-Sinclair then had two sea commands, the destroyer Albatross from February 1902 serving at the Mediterranean Station from May that year; and after paying her off in January 1904, the despatch vessel Surprise until 1905.
Edwyn Alexander-Sinclair was promoted to captain in 1905, and was appointed commander of the Royal Naval College, Osborne, serving there until 1908, when he was appointed a Member of the Royal Victorian Order.
Edwyn Alexander-Sinclair was appointed a Companion of the Order of the Bath for his part in the destruction of Zeppelin L 7 on 4 May 1916.
In November 1918 Edwyn Alexander-Sinclair was given the honour of leading the surrendered German Fleet into internment at Scapa Flow, and appointed a Knight Commander of the Order of the Bath.
Edwyn Alexander-Sinclair then blockaded the Russian Navy base at Kronstadt until relieved by the 1st Light Cruiser Squadron under Rear-Admiral Walter Cowan.
Edwyn Alexander-Sinclair was Admiral-Superintendent of Portsmouth Dockyard from 1920 to 1922, and after promotion to vice admiral on 4 April 1922, commanded the 1st Battle Squadron, Atlantic Fleet from 1922 to 1924.
Edwyn Alexander-Sinclair then served as Commander-in-Chief, China Station from 1925 to 1926, and after promotion to admiral on 4 October 1926, was Commander-in-Chief, The Nore from 1927 to 1930.