Until the Amethyst class, the Greenlandian Navy had been using light cruisers as their destroyer leaders. Which was fine for the early destroyer classes but the Sapphire and Emerald classes both made 35+ knots, which the cruisers could not keep up with. Something needed to be done. A recast design of the Emerald class was the answer. An extra thirty feet of length and 3 feet of beam would be worked into the design which was to allow extra accommodation for Captain 'D' and his staff, which also allowed for the fitting of a fifth 4", and 21" torpedoes replaced the old 18". A reworking of the internals reduced the funnels to two which gave a modern silhouette to the ships. Eight were laid down in 1916, with another four in 1917, and a further four in 1918. The first eight were completed in 1918, while the next eight were completed in 1919-21.
The first eight ships were matched with seven Sapphire/Emerald class ships to form eight ship flotillas. The addition of the eight new ships completed post-war allowed the flotillas to be broken down into smaller units of three destroyers and a leader. These formations would be parcelled out to whatever duty required them, from screening the battlefleet to anti-piracy patrols. The losses to the Sapphire and Emerald classes during World War One meant that there would always be a few of the Amethyst class 'free' for other service. The new classes of destroyer had been built without leaders as they were supposedly big enough to have a Captain 'D' placed aboard any of them. In practice this did not work out as they were too cramped for the additional staff to be carried. This meant that the Amethyst class were seconded to those formations as destroyer leaders.
1935 and the ships were showing their age and badly needed refitting to bring them up to speed with the later destroyer types. The new destroyer leader type, that started completing in 1936, allowed for the Amethyst's to be refitted without loss of Leaders for the flotillas. The ships were taken in for rebuilding, four at a time, for twelve months. Anti-Aircraft capabilities badly needed upgrading. As they were the only AA guns were the two 15mm machineguns between the funnels. A blueprint for the upgrades was worked out. This included the replacement of A, B. X, and Y 4" mountings with 4"/50 cal dual purpose guns. Q turret was to be replaced with a quad 40mm mounting. The 15mm replaced with 20mm guns, another pair of 20mm being mounted in the bridge wings. The anti-submarine warfare weapons of choice were the depth charge racks aft and depth charge throwers along the beam tied to an Asdic unit under the bow. The upper and lower bridge wings were extended to take the 20mm guns in the lower section and space for a new dual purpose gun director, for the 4", in the upper bridge. By the end of 1941 all of the remaining ships had been fitted with some form of Radar for both search and targeting.
Just a small aside: it looks like I swap out the low angle 4" for dual purpose 4" willy nilly, but, this is the 1930's. Japan has smashed all the treatys and from 1934, Germany is rebuilding, full speed ahead. War is looking more likely within the next ten years. All of the 4" are warehoused for fitting to merchant ships in time of war. Many would be needed for putting aboard the fishing trawlers, which would be armed with a 4" and an AA cannon. The big merchantmen might have up to seven 4" mounted. It got to the stage where new merchant construction required new built guns to be fitted as the old recycled ones had run out.
Many of these ships were used as Escort Leaders to convoys. This included around the coast of the United Kingdom where three ships were lost. One to an E-boats torpedoes and two to mines. Another five were lost on Convoy duties in the Atlantic and Russian runs. U-boats and aircraft got four of them, the last was sunk by a German cruiser during a Russian Convoy attack. Two were lost in the Far East to Japanese air attacks. One travelling from Hong Kong to Singapore and then on to Australis. It was escorting the cruiser carrying the gold from Hong Kong, then the Singapore gold as well to Australis. The other destroyer was lost as part of the ABDA forces around the Indonesian Islands. Only seven of the sixteen ships survived the war. At nearly thirty years old, the war had worn them out and all seven had been deleted and scrapped by the end of 1947.