Chrysolina americana...

Or Rosemary Beetle in English. First recorded as established in Britain in 1963 so its been around a little longer than me. They feed on rosemary, obviously, but also lavender, which is what this little chap and his friends were doing at Teddington Lock (as the extra shows). Didn't have the macro lens unfortunately and the wind made it rather hit and miss, so this was as good as I got.