It was an empty leg of a horse flight, there were grooms on board. It might well have been carrying newspapers. Fortunately it was my night off!
But we were on then - one of the very few times my husband and I were ever on watch together! There were three of us in the Tower chatting and watching it come in, realising as you do that it seemed to be ... oh my goodness yes it was too fast, our conversation slowed to a halt amidst a sudden rush for the crash alarms. Very fortunate crew and no horses. Slight damage to an ATCO racing upstairs from the rest room, trying to get his trousers on and ending up with "both legs down the same knicker" - he fell over the step!
Ah those were the days!