Thank you all for weighing in on this. I really appreciate the advice and I am going to start walking with my key in my hand and try to get a rape alarm. Not just for this guy, but because I walk alone most of the time and it is a good idea.

An update: the morning after I wrote the initial post I waited an extra half hour before leaving the house, but I couldn't wait longer because I had a meeting at work. I was hoping to walk with my housemate, but couldn't wait. I got past the place where this guy usually waits and he wasn't there so I continued on - fast. I thought I had got past him, when he came running after me. I was very tense and tired and I am afraid I became quite rude. I kept saying "you are freaking me out" and "I don't like being followed". He asked for my phone number. I just totally lost my temper and shouted at him that I will not give him my phone number. I sincerely hope that he got the message, but in the meantime I have spoken to my boss and I now wait for my housemate, no matter how late he leaves. I will do that for a while, but I can't lock myself in the house indefinitely. My housemate visits his girlfriend on weekends, and I have to go shopping.

I really hope this is over now. Thanks to all of you. It is sometimes hard to listen to your intuition, because social conditioning takes over. But I think this is a good time to learn to pay more attention to that inner voice.

Many thank you's