Happy to be drafted!
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On Stefan's question, the Cruiser tanks were as big size-wise as Germen mediums, but the early ones (A13 Mk.III & Mk.IV) certainly had "light tank" armour of only 6-30mm thickness! And the early 2pdr guns were certainly in the light tank camp. Also, they were fast, designed for rapid movement to exploit breakouts. The real problem is that the British didn't think in terms of "light" tanks as a class (part of why the Vickers series sold so badly), but instead thought in terms of "cavalry" vs "infantry support" functions regardless of size. On the basis of armour, speed, and armament I'd be tempted to vote "yes", but nothing later than the A13 Mk. IV - the later Crusader etc were too close to all-rounder mediums for my liking.
Tom