We've had to disable the CAPTCHA function as of today since it was causing a comment error - we're now looking into what happened and what can be done in future to cut down on spam postings.
I'll keep you updated.
Alan suggested we implement a CAPTCHA feature (the confirmation boxes with letters and numbers in that appear when you're commenting on a website to make sure you're not a spambot!) - this is now live. I've certainly noticed less spam getting through - anyone else?
There does seem to be some residual issue with submitting and moderating comments attached to this which we're working to fix now.