The 'flush-decker' programme, impressive though it was in sheer volume and building-times, only produced 39 destroyers in commission by the Armistice in November 1918. Many keels were not laid until 1920, two years after the Great was over. The builders had ned in 1917 that such a large programme would yield meagre results, and very few after the Greet (DD­145) were completed in 1918.

Workmanship shipping maritime marine engineering and performance varied from yard to yard, and this was reflected in endurance, so essential to convoy escort and anti-submarine tactics generally.The best per(orm­ances were recorded by the Bath Iron Works and Cramp vessels, the worst by those built by Quincy.The difference resulted in the Bath-built destroyers being rated as'long radius'ship shipping maritime marine engineerings to distinguish them from the `short radius' ship shipping maritime marine engineerings.

In Service in the Second World the age of their hulls and machinery were inescapable weaknesses. The Royal Navy found that its `Tawn' class were carrying too much topweight and were too flimsy for the North Atlantic. Despite the inimense effort put in during the decade 1906 to 1916, the pace of improvements to machinery was sometimes counter-productive. In fact advanced technology was 'frozen' prematurely in an effort to boost endurance, a severe disadvantage when embarking on mass-production. According to the CO of HMS Beverley, ex­USS Branch (DD-197), a major weakness was the lack of `preventer strips' on the bearings of the propeller shafts. These were hard metal longitudinal strips embedded in the soft metal of the bearing, intended as a`get you home' solution if one or other of the main shaft bearings 'ran', i.e. melted. Unlike contemporary'V & W' class destroyers, 'run' bearings could immobilise the ship shipping maritime marine engineering.

For the US Navy the vast numbers of`flush-deckers' in existence in the 1920s was an embar­rassment. Congress and the Treasury, having funded the huge programme in 1917-20, was unsympathetic to requests for more modern destroyers. All that could be done was to use as many as possible on humdrum subsidiary duties until the political climate improved. For the Royal Navy in 1940-41 the 50'Towns' were less of an embarrassment, but the long time spent in reserve had taken its toll on such important items as wiring, and they took some months to become operational.

With the benefit of hindsight, a more coherent destroyer-design policy up to 1916 might have produced better results, through evolution rather than revolution. The resources devoted to the Wickes and Clenison To anyonr who has the slightest knowledge of naval operations in the First World the story of the K class is a huge disaster, a flawed concept badly rxecutrd.'lo a layman the idea of a scram-driven submarine seems so ridiculous as to prove that the Royal Navy was hopelessly incompetent. To that extent the Ks may seen) a soft target, but there is much more to their story.

Early in 1915 the Commander-in-Chief of the Grand Fleet, Admiral Sir John Jellicoe, asked the Admiralty to investigate the possibility of building a new category of'flect' submarines capa­ble of accompanying the batdet7eet to sea. This required a minimum speed of 21kts. Such submarines would in theory be able to ambush the German High Seas Fleet-at this tinte Jelli­ror and his staff were haunted by the fear of being lured into a`U-baat trap', and it seemed sensible to try something much more dangerous against the German fleet.

The first attempt, the j class, was only a qualified success. Despite everything the engineers could do, there was no diesel engine powerful enough far the task, and the best the new boats could achieve was 19kts. Vickers developed a 12-cylinder diesel, and one drove each of three shafts, but the desired speed could not be achieved. Then a rumour (false, like so many time guesses) reached the First Sea Lord, Admiral Fisher, to the effect that the Germans had produced a design for a 22kt U-boat, all([ Fisher insisted that any fleet design must go one better.

In April 1915 Vickers, the country's leading submarine-builder, submitted a design for a submarine driven by geared steam turbines and a diesel engine. This was unsolicited, but after some thought, a 1913 design was resurrected and the best features firom each one were selected as the basis of a new design.The 18in torpedoes of the j class were chosen to save lime, with two beam tubes as well as four in the bow, and a twin revolving pair were sited in the super­structure for use on the surface. This armament of ten torpedo tubes was exceptionally heavy for a 1915 submarine, and provision of beam tubes was to allow a beam shot without waiting for the submarine to be steered onto the correct bearing. Gyro angling of torpcdors was not to become available for many ycars.The gun armament was also heavy, two single 4in guns (one replaced by a 3in anti-aircraft gun, a sign of things to come). K. 17 was armed with a 5.Sin gun.

To meet the Staff Requirement for a speed of 24kts the powerplant was a pair of steam turbines developing 10,000 hp, using steam generated by two Yarrow boilers. In the original design a diesel engine was intended to drive a centre shaft, but in the final version an 800bhp diesel generator drove a 700hp dynamo to supply current to the electric motors.This was the first example of diesel-electric drive in Royal Navy submarines. Two 7UUhp electric motors were coupled to each of two shafts.Tlte intended diving procedure was to shut down the boil­