Mystery caterpillar

[bugboy]

This one is causing me to scratch my head. Found last weekend in Abbots Wood. I presumed at the time it was a Knot Grass Moth Acronicta rumicis but when comparing it to pictures in my books it didn't look quite right and further research would seem to rule it out based on the species lifecycle which hibernates as a pupae and is single brooded, meaning adults are on the wing now, not fully grown larvae. It does look a bit like a Brown-tail too but again not enough to convince me... any ideas?

[Allan.W.]

Bit of a puzzler that one Bugboy ,like yourself ,first thoughts …………...Knotgrass ,but looking at it more closely ,I think not ,
pretty sure its not Brown Tail ,it looks to be on Sallow ,did you notice if it was feeding ?it also looks fully grown ,possibly wandering to pupate
shame you never boxed it and bred it through . Regards Allan.W.

[Butterflysaurus rex]

Looks a bit like a late instar Small Eggar.