The machine reads a postcode off every letter and drops it into a bay for its district, and the bays are numbered from the district list, which is maintained centrally and does not contain districts that no longer exist. Bay 61 is not on the list. It fills every night with mail the machine has read as belonging to a district that was merged away in 1996, and the mail is addressed there.
I am a machine operator on the night shift, and the bays are where my night ends, because I clear them.
How the machine sorts.
Letters go through a reader at about ten a second. The reader finds the postcode, looks it up in the district table, and the letter is gated into the bay for that district. The table comes from the national database and it is updated when districts change, and when a district is withdrawn its code is removed and mail carrying it is gated to the manual bay for a person.
There are sixty bays on our machine.
Every night the machine fills a bay 61.
There is no bay 61 on the machine. There is a chute at the end of the run that was blanked off when the machine was shortened in the nineties, and behind the blanking plate there is a tray, and in the morning there is mail in it.
The mail is addressed to a district code that was withdrawn in 1996 when two districts were merged, and the machine's log shows each item read, looked up, and gated to 61, which the table does not contain.
The blanking plate is bolted on. I have taken it off and put it back on with new bolts and a smear of paint across the joint, and the paint is unbroken in the morning and the tray behind it has mail in it.
What has been checked.
The table. Reloaded from the national database, which does not have the code. The machine's software, reinstalled. The reader, recalibrated.
The mail. It is real mail, posted in the town, with real stamps, addressed by hand to real streets with the old district code, which some people still use, and which the table maps to the new district and which the machine, for these letters, does not.
Not for all letters with the old code. Most of them gate to the new district correctly. Bay 61 takes a handful a night, and I have compared them, and the ones that go to 61 are all addressed to streets in one part of the old district, the part that was cleared for the ring road, where none of the streets exist.
The addresses.
I have walked it. The streets on the envelopes are under the ring road and its embankment. The house numbers on the envelopes run higher than the streets ever did.
I have opened one, under the undeliverable procedure, and it was a bill, a real bill from a real company for a real service, addressed to a name at a house that has been under an embankment for thirty years, and the company, when I rang them, had the account, live, paid monthly, by a card in that name, and would not tell me more, and should not have told me that.
What is done about it.
The tray behind the plate is emptied by me in the morning and the mail goes to the undeliverable section with a code that means address does not exist, and from there it goes where undeliverable mail goes, and I have stopped opening them.
The machine's log shows bay 61 and the audit flags it every night as an invalid destination, and the flag is cleared by the day supervisor, who has done it so many times that it is a keystroke.
What I do.
I run the machine and I clear the bays.
The one thing I have changed is that I clear the tray behind the plate before I clear the sixty, rather than after.
The reason is a morning in the winter when I cleared the sixty first, and came to the plate last, and took it off, and the tray was empty, and the machine's log showed a handful gated to 61 in the night, as always, and as I stood there with the plate in my hands a letter came down the chute. One, from a machine that had been stopped and powered down for an hour, down a chute that connects to nothing, into the tray, addressed to a house under the ring road, and it was warm from the reader, and the stamp on it had not been issued yet.