Unexciting caterpillar

I have only run the light a few times since last posting, adding Early Grey to my slowly-expanding year list. But this caterpillar or grub joined me in the garden and, needless to say, is beyond my powers of ID.  The thing which looks like a telescope is a felt-tip pen which I hope gives some idea of scale.  Many thanks for any help and meanwhile, hoping for warmer nights.  Martin Wainwright, Thrupp, Oxon