Well, those crossed fingers did the trick. After a series of very chilly days (and a couple of frosty nights), followed by two really warm (but sunless and windy) ones, things returned to a more sensible footing today (25th). The sun shone, the breeze was more gentle, and in sheltered spots it felt pleasantly warm.
Clearly the Red Admirals thought so too - I counted four individuals around my local patch, including these two. Dave