Vapourer eggs at Uskmouth

Tara from RSPB pointed this Vapourer cocoon covered in eggs to me. Its on an NNR sign at 

Uskmouth. She spotted the wingless female and a male mating on the cocoon a couple of weeks ago. The sign is approx 15m away from the nearest potential food-plant, a sallow, so the newly hatched caterpillars  will have quite a trek to make when they hatch in the spring.