Captain Armstrong was my wife's step-mother's brother (my step uncle in law?).
He was an up and coming RN officer in WWII, with both fame and family connections (his brother commanded the royal yacht and Winston Churchill personally called his father back from retirement to command the Royal Navy's navigation school). He was pegged as a possible future First Lord of the Admiralty by his contemporaries until he got himself killed off the Anzio beaches while making the last U-boat kill in the Med. After 24 hours of depth charging, U-223 surfaced in the dark and tried to make a run for it under fire from Laforey. The U-boat fired a T-5 homing torpedo from her stern tube which blew up HMS Laforey, killing most of the crew, including Capt. Armstrong. (Laforey's 'foxer' had been expended by a acoustic torpedo hit on it during a previous action) U-223 was badly damaged by depth charges and gunfire and was abandoned on the surface but her work for the night wasn't finished, circling around and running over many of her crew as they floated on the surface.
Armstrong demontrated his command ability in Insect Class river gunboats (Cochafer and Cricket) on the Yangtze River in the late 30s. Prior to that he commanded the Sloop HMS Fowey. He entered WWII in Command of HMS Wren, an old leftover from WWI with a gaelic fisherman crew, only a fourth of which spoke English, but they were good seamen. Wren fought off Norway and in the evacuation of France. He impressed with his ability to develop and train a crew and was given command of Maori in 1940 (three months before Wren was sunk in the channel by the Luftwaffe). While in command of Maori, he also had command of the 2nd division (Maori and Piorun) of Vian's 4th Destroyer Flotilla at the time of the Bismarck chase (they were escorting troop convoy WS-8B around Ireland when called off to escort Tovey's capital ships). Until the 1950s he was credited with a torpedo hit on the Bismarck during her last night [a post war German account claims that there were no torpedo hits... that a foc'sl fire broke out on Bismarck from one of Maori's star shells landing on the deck, at the same time Bismarck lost propulsion in a drive train jam during one of the many prop reversals used in attempts to steer Bismark - it appeared to the British that an explosion (Bismarck's gun flashes) at the timed arrival of Maori's torpedoes started secondary fires (German claims of Maori's star shell landing on deck) and stopped Bismarck dead in the water (German claims of propulsion malfunction)] Some references still credit the 4th DF with two hits on the Bismarck. There has never been definitive evidence, one way or the other... but based on the circumstances of the battle, the odds are against a successfull torpedo hit, much less two.
After the Bismarck action Vian was promoted to Admiral and Armstrong was promoted to Captain (D) and given HMS Onslow and the 17th Destroyer Flotilla (mostly still under construction in the yards) to develop and train. He commanded the 17th in Commando raids on Norway, escorted convoys to Russia (destroyer escort command of PQ-18), provided cover for the Torch landings and was credited (Onslow) with one confirmed U-boat kill (during PQ-18) . About six months after his transfer to Onslow, Maori was sunk by the Luftwaffe at Malta.
His greatest achievement was the Bristish victory in the Battle of the Barent's Sea. Unfortunately, he only received 'informal' credit. At the end of 1942 he was given a staff command position in Coastal Forces, his Captain (D) position taken by Capt. Rupert St. Vincent Sherbrooke, a descendant of the famous Admiral St. Vincent. In the Barents sea battle, a small force of destroyers successfully protected convoy JW-51B from the heavy cruisers Hipper and Lutzow and six German destroyers long enough for the cavalry (HMS Jamaica and Sheffield) to arrive and beat off the German force. The british destroyers were battered and Sherbrooke greviously wounded early in the battle. HMS Onslow survived, barely. The battle was a 'soldier's battle' with the Captain (D) severely wounded early on and command transferring four times from one destroyer to another as they were each knocked out of action. Even though Sherbrooke displayed great bravery and provided a great example, it was the training and discipline and esprit de corps of DF 17 that won the battle. All the work of Capt. Armstrong. Sherbrooke had been in command for little more than a month, and had not even met most of his Commanders in person by the time of the battle. But the propaganda value of Sherbrooke was immense, here was a descendant of St. Vincent, wounded like Nelson (loss of an eye) showing incredible bravery against unsurmountable odds, a direct link to the old Navy traditions and mythology. Sherbrooke got the Victoria Cross and Armstrong got a training command in Coastal Forces.
At the end of 1943, Capt. Armstrong was given HMS Laforey and the 19th Destroyer Flottila in the Med. Laforey battled U-boats, guided bombs and E-boats off the Italian coast. After leaving his three prior commands shortly before each was sunk or heavily damaged, Captain Armstrong's luck ran out while battling U-223 off of the Anzio beachhead.
After the war, like after most wars, most heros (dead or alive) faded from memory. Unfortunately the only newsworthy item after the war was the scandal when his American born widow (an heir to a Department Store fortune and classmate of Catherine Hepburn) remarried, to a German prisoner of war, an enlisted man, no less. Interestingly enough, the German's passing last year rated a half page obituary and photo in the Daily Telegraph. Probably the press's first reference on Captain Armstrong in 50 years.
Anyway, back to the question.... I'm writing a biography for the family and am looking for references. I have dozens of books that refer to him and have been able to piece together a fairly good outline of his career. I have found numerous references to his 'valuable contributions' to developing 'Coastal Farces' into a credible fighting force against the E-boats, but have found no specifics yet as to what he actually did.