When I Iived in London in the late 80's to mid 90's and fished Bewl, Weirwood and Pitsford reservoirs, wet fly fishing with Soldier Palmers, Grenadier, Wickhams, mini muddlers etc. was still popular. A friend of mine who I fished with then, who lives in North London and still fishes the Midland reservoirs saw a change after the hot summers of the 1990's. Fly species such as olives and sedges declined after falling water levels during droughts. At about the same time the blob became popular. My friend and I'm sure many people on this forum noticed the lack of some fly hatches to bring trout up to the surface, a change to newer flies like the blob, methods like the washing line etc. and fewer anglers using a floating line with wet flies on Midland reservoirs.Good question, main reason I suppose is that I moved onto other waters where buzzers and other nymphs were more productive. I rarely fished Brenig or large stillwaters in the 90s and 00s.
I remember I had a day on Rutland in the 80s and the fish went mad for an Invicta, but unfortunately they kept breaking me.