Yes, incredibly, the Knepp Purple Emperor season is very much on the wane, already.
I did the Knepp PE transect today. I expected to see 25-30, but struggled to count 11 in perfect weather conditions (last week's count was a record 80).
They've plummeted.
However, it's clear that males aren't occupying territories much in this heat, so I probably under-recorded.
Also, both sexes are clustering around 'feeder trees' producing oak sap, and there are few of those along the transect route this year.
One tree in particular is proving immensely attractive, with 2-6 adults (both sexes) ever present. There are 51 people in this photo, admiring Emperors getting plastered on Patrick's Tree -
Also, Empresses have the habit of going shading in hot weather, often for long periods. Here's a middle-aged female who went shading in a bramble bush for over an hour today -
My advice is don't travel long distances to visit Knepp this year, and don't come at all after the coming weekend, they'll be over. If you do come, visit Patrick's Tree, along the White Route (but note that it doesn't function in a SW wind).