The Halcyon class and purpose-built minesweeping

What was the Royal Navy's first purpose-built minesweeper class?

The interwar Halcyon class is the stronger answer, after an earlier reliance on converted trawlers.

Vessels employed in minesweeping were different from ships designed around that task from the outset. Converted trawlers dominated the earlier British story because they could be adapted rapidly with towing gear. The evidence does not support naming a clear First World War purpose-built Royal Navy class. The interwar Halcyons provide the stronger answer because minesweeping shaped their design from the beginning. Purpose-built minelayers followed a different development timetable.