Bugs in my leeks

Started harvesting my leeks and found they have quite a few little brown bugs (about a mm long), that have burrowed under the skin; one leek had about 8 and by the time I'd peeled off the layers to get rid of them all it was about the size of a spring onion. The tops of the leaves look pretty chewed up as well.
Could someone tell me what these are?
Thanks!

Thanks!
Yes, it's the allium leaf miner, the RHS photo makes it clear - though seeing them that close up makes it worse!