Mystery solved

Decided to repot a tomato plant which was in too small a pot and beginning to struggle – and saw this when I got it out of its container:

I carefully picked it out, to find that it was a row of carefully wrapped leaves, containing some sort of pupae

I’d got no idea what could have done this – but the wonders of social media meant that I got an answer fairly quickly – a leaf cutting bee! Which also explains the strangely cut out leaves on lots of my flowers…
We’ve put the pupae in a container in the greenhouse and hopefully it will still manage to hatch out (if that is the right technical term!).