Hi, Thank you for your question and welcome. My name is ***** ***** I will assist you. The fact that he physically assaulted and defamed your business in public gives you grounds to say the contract with him was terminated. I would write back to him as follows:
(i) Say you deny any liability for the money, and say that he released you from liability when he physically assaulted you;
(ii) Say that from his conduct he terminated the contract and if anything he is liable for damages for breach of contract and for defaming his business;
(iii) Say that his attempts to demand money from you amount to harassment and a criminal offence under S.40 of the Administration of Justice Act 1970;
(iv) If he does not drop the matter you reserve the right to counter sue him for breach of contract and defamation;
(v) Say you have not decided as yet whether to report the physical assault he committed on you to the police but reserve the right to do this also.
On a side note I would take this opportunity to write the outlines of a witness statement and get any confirmation of other witnesses.
If he drops the matter do you still want to sue him?
Kind regards AJ