How do I stop a persistent suitor

Advice above all good - sorry you have all this hassle. Suggestion to use a male relative or friend to go round is a very good one. Good luck.

Do you have a male relative who could have a word with him and reiterate that you are not interested. It's unfortunate that some men of our generation consider a woman alone as weak and vulnerable and will only back off if he knows there is a man in the background. As others have said keep a record of any contact between you and copies of your letters telling him you are not interested.

Yes this does amount to stalking and he needs to realise that he risks prosecution.
Record everything, keep copies and see a solicitor - or even go straight to the police.
He may be a harmless old duffer, but his behaviour is verging on harassment . There is a fine line between what is acceptable and not, he seems to have crossed it.

Yes to notifying the police and logging his approaches as anno says. A friend of mine had this problem a few years ago after her husband died. She met a man through mutual friends, went out for meals with him a few times but then told him she didn't want to take the relationship any further.

Before long, he was seriously stalking her. She eventually had to get a restraining order which worked for a while but when she met someone she really did want to stay with it all started again.

Don't leave it too late before taking action.

You need to keep a copy of any letter you send him, and log all his annoying approaches. If you need to notify the police, you will have evidence to show them. There is a fine line between pest and stalker and I'm not sure when one escalates into the other. Good luck in getting rid of him.

You've told him clearly and bluntly that you're not interested. He's not taking no for an answer. If he contacts you again, send him a letter by recorded delivery telling him in no uncertain terms that you are not interested, you do not want him to contact you again and if he does you will contact the police. Recorded delivery means he cannot deny receiving this letter. If he contacts you again he is stalking you. Contact the police and let them visit him to warn him off.

Keep a record of every contact.

Do you have a solicitor who could write him a stern letter threatening police involvement or just ask at a police station for advice.

It could be. I am not sure about these sort of cases. But local gossip has it that a retired policeman, has had a restraining order out on him as he was "stalking" a local lady. Not sure how bad it got though.
Would citizens advice be any good?