Larva on Yellow Rattle

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I found this well developed and quite distinctive green caterpillar on a Yellow Rattle plant in my garden. I haven't managed to identify it and the only species I can find associated with Yellow Rattle is Grass Rivulet moth, which I don't think it is.
Anyone recognise it?

[Matsukaze]

Mouse Moth would be a good candidate.

[Part timer]

Thanks, Matsukaze. Looking at images of the larva on the Web, I'd agree.