Indeed so, it was happening much too often and one day in pouring rain, they finally mutinied. It happened several times, and even the presence on one occasion of (lonely) BT Police seemed not to have any effect. It happened far less often in due course. I recall in the Army that the tradition was to make sheep bleating noises in similar situations. Somebody had indeed taken notice, as one passenger said at the time 'even worms can turn'.