I have introduced, temporarily I hope, comment moderation.
It hasn't gone down too well with one unwelcome guest who writes:
Oh by the way Simon crippling your blog by comment moderation means I will wait until your blog slowly dies and you remove it. Too much hard work for you - suits me. Merry Xmas.
I think this blog will survive. Oh, and Happy Christmas to you too!
PS. The Internet really brings out the best in people, doesn't it?