I've discovered the error, which lay partly with me.
See, there are two types of "pipe" , the broken (¦) and unbroken (|).
You may have noticed that the instructions I gave you previously produced a ¦, which doesn't work because it's not exactly the right character.
The error lay partly in my not realising they were different characters, because back in my early days of DOS, and even the XP command prompt, display the unbroken pipe as broken.
The rest of the error lay with the keyboard layout image I found via Google, which displayed an unbroken pipe on AltGr+1.
But, I switched my keyboard to Romansh, and pulled up the OnScreen Keyboard in the Accessibility options, fired up UO, and for some reason I can't understand, what should have been AltGr+1 switch to the key to the left of it.
Not that any of that matters, because it was the broken one, anyway, which doesn't work.
However, I did catch a peek of a distinctly pipe-looking character on AltGr+7.
On the off-chance you were sensible, and sisn't read through my tale of sadness, I'll add it again here, the TL;DR version:
AltGr + 7