Final update from me: I received my supporting documents back, nine weeks after my British passport was printed and eight weeks after it was received (13 weeks after application). I had paid extra for secure delivery, but the documents were sent via ordinary Royal Mail and pushed through the letterbox (despite living in a block of flats, which I know is a no-no for ordinary passport delivery).
I did not receive any notification in advance. Per the tracking information, they were posted yesterday. No idea if this was linked to my increasingly angry complaints – the last of which I made on Sunday, specifying that I don’t need another callback from customer service, I needed someone in Peterborough to physically find and post the documents.
There were two barcoded labels on the envelope with my name and address – one for Royal Mail, and one general. Not sure if this is an internal barcode, or it was supposed to be for TNT and this was physically out of that stack and mailed via Royal Mail instead.
I am curious if I get any further callbacks from the passport office (no one responded to my last call, or my last written complaint) and if they even know they’ve mailed the passports back. My naturalisation certificate was crumpled and dissheveled. I might have cared about that six weeks ago, but at this point it’s the least of my problems….
Glad this clusterf*ck is over! Good luck to all who are still waiting for the return of their documents.