And kids today seem to learn that the only two British aircraft in WW2 were the Spitfire and the Lancaster (and possibly the Mosquito) - the Hurricane and the Tempest just don't get the same share of mindset.
The Tempest was, I think, the last production aircraft to use a sleeve valve engine. With the relatively primitive production facilities of the 1940s the sleeve valve could produce more power than a poppet valve design owing to the lack of (and limitations of) the hot exhaust valves of the poppet design. It was a pity that by the time Napier got serious about its engine and started making it properly the end of the War was in sight and the jet engine was already taking over. Whatever the reason, the Tempest shot down a number of ME-262s - though these were so unreliable that if the Germans had enough fuel to keep them up long enough, the engine would eventually blow up.
[edit - oh yes, excellent article. If we are very good please can we have more like this?]