Learn To Lock The Door

This happened four years ago about a month or so after I had turned 18.
My parents had gone away for the weekend leaving me free to use the big TV to cast pork to off my ipad.
So on the Saturday afternoon I was lying naked on a chair masturbating, I had the sound turned up and was totally engrossed in the action on the screen.
It was therefore a shock when the door to the lounge opened and my mum's friend Carol walked in, she always used to knock but let herself in, she must have had a full on view, she said sorry and left, I just generally panicked.
She gave me time to dress and sort myself out before knocking loudly.
She was very good, told me it was natural and not to feel guilty or embarrassed and she has never said a word to anyone about it, although she still teases me a little about it.