I have a mate i've known for 20 years odd. He's in Edinburgh, im on the Isle of Wight. We meet up a couple of times a year in London, go for a few beers etc etc.
Bit of background.
Wehn i first knew him he was a graduated student trying to find a job, so pretty skint. Then he got a job in a BIG well known global news agency in London on about £35kpa. This is great until he has a nervous breakdown after about a year, so he goes back to Edinburgh and there's he's been ever since.
He's pretty ruined mentally and looks a bit rough, but he's a friend and I stick by him. His medication messes him up quite a bit and although he's still a friend, he's not the same by any stretch of the imgination. He's hard work and can be a bit slow / quiet.
But in the last 6 months, something has changed, he's been really hard to even get hold of, doesnt respond to any messsages, when he does respond, theres no mention that i've been concerned about him.
Anyway we finally managed to meet up in London a couple of weeks ago, even then he's late and wasn't answering his mobile. He was quite unsettled, talking to people as if they were mutual friends from the past, shouting out random abuse to people, making obviously racist comments, giving an Asian glass collector the finger and talking in a false mancunian accent.
I obviously felt VERY awkward and quite on edge, after about 3 hours of this I decided enough was enough, so whilst waiting for a tube train with him I wandered off and got one going the opposite way.
I do feel guilty for just buggering off and abandoning him, but I just didnt want to end up in a situation where i had to physically defend him or myself from someone who took exception to his comments. I know im in the wrong for just dumping him, but it would have led to a confrontation with him.
My main concern is that its pretty obvious he needs professional help, but what can I do? Im not convinced he would actually listen to me. If we lived nearer perhaps I could do something. Most of his friends are now ex-friends because he's managed to alienate or upset them over the years.
Or do I just walk away and draw a line under this friendship, or do I try and communicate with him to say I have concerns over his wellbeing?
I really dont know what to do here.

