I remember the frustration that I would frequently have with the postal service not just in the USA but other countries as well. There was a time that I was mailing a care package across the Pacific to a friend that was studying in Japan and by the time the package got there, the birthday was 2 months behind us. So that means that my package, which I had to pay more postage on than the contents were actually worth, spent at least 10 weeks in transit.
This sort of inefficiency is quite maddening and is probably a big part of the reason why companies like UPS, Fed-Ex, and DHL were able to make a killing simply by guaranteeing that whatever you are mailing ends up there in a timely manner.
I can say that I have never had something like this happen though as a letter has arrived at its destination, with no apology given whatsoever, more than a CENTURY after it was originally mailed.
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It happened in England and the recipient said that he assumed the postal stamp on it, which said "16" was from 2016, which would be odd enough but as it turns out he was slightly off about the real date when it was first mailed.
Finlay Glen didn't originally open it, citing fear of a law that makes it a crime to open mail not addressed to you, but then he started to have his suspicions about how old it was when he noticed that the stamp had a picture of a King, not a Queen on it, and the total postage amount was 1 penny. I don't even know what it costs to mail a letter these days but I would be willing to bet that it is at least 50 times that much.
Glen turned the letter into some historical society and they confirmed that it is in fact over 100 years old.
I'm sure there are tons of mail that is just left sitting somewhere and this is so common that many TV shows and movies make fun of the irresponsible nature of government-run postal service on a regular basis.
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I recall an episode of Family Guy where Cleveland is showing Lois the ropes and how nobody at the Post Office really knows or cares about what they are doing and from my own frustrations with the USPS in the past, I think that this is mostly how we think about the Post Office.
The thing that gets me about this entire situation is that not only did the British Postal Service not do their job for more than 100 years, but when they finally did find the letter the simply delivered it rather than issue any sort of apology or excuse. I don't know a great deal about the U.K. but it honestly wouldn't surprise me if Mr. Glen ends up getting fined for having opened the letter because that is the way our silly world functions these days.