Unknown larva and eggcase ?

Unknown larva and eggcase ?

Observation - Unknown larva and eggcase ?. Description: Noticed the small brown eggcase 5mm long oval shape with lighter band around centre attached to the underside of an oak leaf by a thread. Then noticed what might possibly be a parasitised larva nearby. Any ideas as to what they might be will be welcome.

Noticed the small brown eggcase 5mm long oval shape with lighter band around centre attached to the underside of an oak leaf by a thread. Then noticed what might possibly be a parasitised larva nearby.
Any ideas as to what they might be will be welcome. I have retained both specimens to see what developes.