**you with the face ** - as an HR manager, I’ve dealt with my fair share of employees/building mates who just could not leave a fellow employee alone, even when explicitly told by the employee and/or HR directly.
With those situations I’m not personally involved and have no qualms being the baddie should an employee need me to handle something of this nature. If you’ve got an HR department - use them. You shouldn’t have to tolerate this and if you feel as though you’ll bring bad things or vibes upon yourself by way of being very direct and firm with this guy, express your concerns to HR and ask them to intervene.
It will be embarrassing and painful, I’m sure, but as firmly and nicely as you can muster - just let him know you are not interested. Sometimes employees don’t want me to personally intervene but want guidance on how to handle a pest who is bordering on harassing them but is currently just that - a pest. They don’t want to escalate to a formal complaint but want some guidance on how to put off their pest for good. (Of course, there are plenty of situations where we take action immediately regardless of that due to grave concerns about safety, threats, etc.)
“I understand you’ve wanted to get together for lunch with me for some time now, but I’m not interested and just wanted to clear up any confusion we may have on this. I thank you for your invitations but I’m actually not interested. Thanks for understanding, I appreciate it.”
Something along those lines, whatever you feel comfortable with as long as it’s directly telling him no, not interested, not now, not ever.
He may or may not get the hint, regardless of what you tell him - but when staring down disciplinary action (or reprimand, whatever your organization may do) he may just back the hell off.
It probably won’t solve the awkwardness and ‘bad feelings’ that may go between the two of you - whether you tell him directly or HR does, he may still feel embarrassed/contrite/awkward/pissed/whatever.
In any event, put the company on notice that you are being harassed by this guy, and they will need to take steps to ensure your protection and safety.
Please take care and let us know how this comes out. It sucks - I know.