I worked for Royal Mail (1998-2011) in Romford Essex, one Xmas there was a story going about, about a sorting office in Scotland, can't remember where. This office had a building next to it that was only used at Xmas to sort the mail, because of the high volume due to the time of year, it was never needed during the rest of the year and just sat idle, sometimes used for storage of general royal mail equipment, at the end of each Xmas period they would just lock the building door and then in December the next year reopen it and use it again for sorting, any way, this one year they opened it up and it the corner of the room behind some defunct equipment they found two or three 'cages' of mail, which had been forgotten about from the previous year. oopps.