Hi Newt. Nice to see you back!
I always have a problem with caterpillars on it as being in the brassica family cabbage whites love it. They weren't the problem though, snails were. They had laid eggs at the base and tiny little snails were merrily munching their way through the stems. Surprising really as they are very thick and fibrous. Wouldn't have thought they were particularly tasty.
I treated with organic slug pellets and then earthed the base up a bit. Seems to have done the trick. Thanks for investigating anyway.
Btw that was the first thing I ever posted on this forum.