Once was a pax on a BA Flight LHR to DUX.
Passengers were told not to smoke after several were caught having crafty fags on the floor behind their seats.
They were then caught smoking in the toilet. The steward was furious. Ten minutes later there was a report of a fire in the toilet from somebody droping a cig into the toilet bin.
There was uproar on the flight, with several pax walking around the cabin looking for the culprit. There was almost a lynching. I was scared witless for the remainder of the flight.
There were no arrests at Dubai, I have my own thoughts as to why that was.
I made a formal complaint, recieved no reply, I havent flown BA since.