Have you ever unintentionally broken the law?

I once cycled down an against traffic bus lane in the snow!

I was trying to cycle to work and the roads were covered in snow except where the buses ran. It was snowing heavily and I was going to be late. I didn’t know my highway code which apparently prohibited cycling in such a bus lane (although cycling in a ‘with’ traffic lane was allowed). Long story short, I was pounced on by a young policewoman sheltering in a doorway who told me off in a very nasty way. I was allowed to continue as long as I pushed my bike on the pavement. I later got a caution in the post!