It was the sightings page at https://www.sussex-butterflies.org.uk/index.php which first encouraged me to visit this wood to see Pearl-bordered Fritillaries (PBF) some years ago, with success.
No PBFs on this day but Butterfly Conservation Sussex's Martin Kalaher has emailed to say..
"Congratulations regarding your Silver-washed Fritillary, which was a national first."
Neil Hulme, BEM had confirmed that "Peter Lovett's butterfly is a female Silver-washed Fritillary. The forewing shape is correct for SWF (concave below the apex; DGF is slightly convex), the upperside pattern shows two rows of spots inside the margin (DGF has one) and the characteristic SWF underside pattern can be seen."