Yes, there is a solution, it's called member guest registration, being activated: I think you would find an upsurge in members. Not many clubs allow spam friendly open boards, that also attract negativity .. Even at Banbury, the penny has dropped..
The troll has now registered as a member: with another combination of his silly numbers: Can't be rocket science to report his IP addresses which must be visible from his registration.
IF only it were that simple Neil, every time there is a spam post i ban the IP address, unfortunately these are all unique IPs, we try to delete as quickly as possible at the moment, but can still explore going to registration only if we get overwhelmed