Predictions for the timing of the coming season -
I very much doubt that the Emperor will be on the wing before the end of June anywhere this year.
The first males may appear at the 'early' sites in Surrey and Sussex at the very end of June, but elsewhere the butterfly is unlikely to start before July 5th.
At most sites, peak season seems likely to be from 10th - 20th July, possibly later.
All this, of course, depends on the weather - things may speed up or slow down.
Just now, larvae are feeding up very slowly, hampered I think by cold nights. None of the ones I'm following, in captivity and in the wild, is full grown yet. One is stuck in the early 5th instar, most are in mid to late 5th instar stage, like this -
I doubt that numbers will be particularly good this year, but much depends on weather during the flight season.
Watch this space...