The Mystery Of The Unpaid Postage

On Saturday I got home to find myself at the start of a mystery which I've still not settled for sure. I found a card from the Royal Mail telling me they failed to deliver a letter / parcel as there was unpaid postage due on it. The mystery came from the fact that I was not expecting anything, from anyone. It didn't help that this was a holiday weekend and I couldn't investigate until today.

When I went to the sorting office and saw the letter, there was no sender information and the assistant told me she'd see a lot of these recently, and thought they were advertising. This being the case, I am not paying for junk mail. It did look like it came from a company with the printed address on the letter visible through the window on the envelope etc. I've racked my brains to think what it could be, and have only one thought.

A few weeks ago I bought a Sony eReader on a special deal where I sent away for a free case for it. As part of that, the form had all sorts of opt ins for "spam me" lists. You always get the impression that whoever is processing these claims will "accidentally" lose your form unless all of the "spam me" boxes are ticked. Part of this was signing up online too, so of course I used an email address I never use for anything else, and unticked all of the "spam me" boxes. I do still expect to have to bin those sent with the form. What I do not expect is to have to pay for the junk mail.

I don't know if the letter was from Sony's junk mail department or not. It's the only thing I can think of. To be able to open the letter and find out would mean that I'd have to pay the postage and take ownership of it. Under the circumstances it was not something I was prepared to do. It may have been one of Sony's partners in that promotion, I don't know. It may be totally unconnected to Sony.

Has anyone else in the UK had issues like this where addressed junk mail arrives masquerading as regular mail with postage to pay? If that turns out to be junk mail, is that legal under UK laws?

Update - Mystery Solved

I've gotten to the bottom of the mystery sender. It was Triage LTD, an employment training company I am currently doing a course with. They sent out a whole batch of letters without paying enough postage, most of us had the same mystery.