A great day in Brighton

I had a great day down in Brighton recently wandering around the North Lanes. I stopped off at an excellent cafe - Mange Tout - and started chatting to the waitress. It's good to talk. Suddenly...

She: Can I have your mobile number?

Me: Er, yes.

I thought it was good to remain silent for a short while. I then gave her my number.

Me: The thing is, I'm going back this evening and I know I don't look old enough but I am actually very married. But you can ring if you like. It's good to talk.

She scoffed loudly.

She: You don't understand; it's for track and trace.

Me: Oh.

She: And not by me either - by your government.

My 'phone has yet to ring. I'm not disappointed.