It true what you said about this incident because it's not new to sometimes ago Iused to work for Royal Mail and during my work training I saw one of the Delivery Driver slip a 739 slip true the door without knocking the customer's door and I personally know about and it's very common among the delivery drivers and some lazy post master. Have'nt said some of them did that because they have been in the job for a longer period and the delivery manager can't do anything about it. My best advice is that if this happens againg go straight to the delivery office and report the driver and you ask the delivery manager to reply back to you in writing if not satisfied you can ask the district manager to look at your complaint. Cheers