Sexual feelings towards old ladies.

It was a cold, frosty morning in downtown Gresham, Oregon. I was walking down the street with my girlfriend. My girlfriend needed to have a look in a clothes shop across the street, so I sat down on the bench. An elderly lady, who must have been about mid-eighties, sat down next to me. I looked at her and felt an erection developing. I tried to ignore it. My girlfriend exited the shop, bags in hand. I tucked away my erection and walked away. I needed to masterbate and did so as soon as I returned back home.
I denied to myself I had any sexual feelings towards elderly women until i saw an attractive old lady in the charity shop. I started to talk to her. She was very nice and eventually took her home, when my girlfriend was away on business. I had an amazing time with the lady, and we had nice, hard sexual intercourse.
Is it normal to have sexual intercourse with a lady in her eighties? Is it normal to masterbate over OAP's? Please sensible comments only as this is a sensitive subject. Thanks.