The prototype ML 100 was privately built by the British industrialist Noel Macklin, who placed an order for this craft on 27 July 1939 with Woodnut's boatyard at St Helens.

Shortly before the Second World War the British industrialist Noel Macklin submitted to the Admiralty an innovative plan for the series production of a motor launch (vessels for harbour defence and submarine chasing).

The hull was to be made of plywood frames divided into nine watertight compartments, with double diagonal mahogany planking forming the outer skin.

The final design was a 110-foot, hard-chine boat of planing form, optimised for speed at the expense of range as befitted the intended coastal sub-chaser role, although the turning circle would be larger than hoped for as a result of the hard chines.

[2] Their role was to be anti-submarine escorts in coastal waters, but, once the better Fairmile B motor launches began to enter service in the autumn of 1940, the Type A boats were converted to minelayers.