Would you report a crime if you see it?

I just saw a robbery!! It was crazy as hell!!! I was walking and minding my own busines, and saw these two chavs stealing a huge smart TV from an open delivery van and run away with it!!! I was shocked to see that in broad daylight but I did nothing, I felt bad for the delivery guy he was very big and seemed naive didn't even know his van was open, my husband said you have no obligation to do anything about it.