Your solicitor should issue a cease and desist letter to him threatening court proceedings if he doesn't stop this behaviour. If he continues thereafter your option is to take him to court for defamation. That could be expensive but you would seek costs from him and the threat of this may be enough to stop him. Happy to discuss. I hope that helps. Please leave a positive rating so that I am credits for my time.
Yes, you could have googled it if you wanted to in the same way that you could have googled how to bomb America. So tell me what you would like to know because the answer to your question is in fact correct. But let me know what isn't as full as you needed and I will try to help you further.