In reply to LeeWood:
> Holly leaves are (quote) 6-8cm length. Therefore by scale observed the nest would be 18-24cm.
> But the raven doesn't normally build in a tree.
And raven nests are
much bigger than 24cm across (OP said 30cm, still too small). I've climbed through the remains of a raven's nest on Ben A'an and it was huuuuge! They're big birds, not just "a bit larger than crow": BTO says they're 50% longer and weigh at least twice as much as a crow.