A variety of acorns?

I picked up these tree seeds several weeks ago when out for a walk. They were green then. I reckoned they'd come in handy for a blip sometime, and I've had a fairly busy day today so this has proved correct.

I'll have to show my ignorance in that I'm not sure exactly what kind of tree they're from. They look very like acorns but the partial covering doesn't look quite right. If anyone knows (I''m sure you do) please put me out of my ignorance! Thanks in advance.

PS. My Editor has just looked in her tree book and thinks it may be hazel (?).