I spent about 45 minutes before work today at Long Valley Wood which is on the opposite side of the Grand Union canal at Croxley Common Moor. I read somewhere that Purple Hairstreak can be found here. No luck with the Hairstreaks but a good few butterflies were on the wing; Peacock, Red Admiral, Comma, Large White, Small White, Green-veined White, Speckled Wood all in or around the wood and Common Blue and Meadow Brown on the moor. Also noted from the canal towpath a Silver Y moth kindly identified by Samuel P.
Silver Y moth-Grand Union Canal at Croxley Common Moor