Thank you all for your comments, needless to say I am embarrassed and ashamed and if I hear nothing I have been very lucky.

I agree except for the reasoning behind her taking down my license plate number, also she wasn't in a uniform so I thought she might have been a plain clothes police officer.

Yesterday I was in my local M & S store and I bought groceries and to my shame I was going to steal 2 items of underwear but I decided against it and put them down on my way out. I was obviously being watched doing this as I got into my car a woman came and stood in front of my car and typed my registration number into her phone. I was dismayed by this and as I drove out of the car park this woman and the security guard were talking and looking at me from the front of the store. What I am terrified of is being contacted by the police as I have to admit I have previously walked out of the same store not having paid for my groceries and I am guessing this will have been caught on camera. Also the car I was driving is my daughters and I would be horrified if she was contacted over this.