I've just finished Game Of Thrones.

Not the boxset, because that would be too easy and hardly worth bragging about. No, I mean the thing that's the same shape as the boxset but which takes considerably longer to plough through. There are 780 pages in all not including the appendix, which is where you turn to figure out if Aegon The Conqueror and Aegon The Dragon are the same person (they are), whether Balon Greyjoy is both King Of Salt And Rock and Son Of The Sea Wind (he is) and how old Danaerys Targaryen is at the start of the book (too young to be doing what she does with Khal Drogo on page 103, at least under UK law).

However, the question the appendix doesn't answer and which has intrigued me most as I've turned page after page is this: what is boiled leather?

Seriously, the stuff is all over the book. The first mention comes on the second page of the prologue and from there on it's never-ending. It usually seems to be worn under armour or ringmail, though I'm intrigued to learn from the fact-tastic Game Of Thrones Wiki site that one Asha Greyjoy wears boiled leather "smallclothes". I haven't got to her yet, but I'm already looking forward to it.

"Winter is coming" people keep saying. But it hasn't actually arrived yet, at least not in the book I've read, so if boiled leather is something to do with staying warm, why don't they save it for when the weather turns really nippy? As my mum would say, they'll feel the benefit more.

My best guess about boiled leather is that it's useful for the same thing wool is when you put it on a hot wash - it shrinks and goes hard so you can make sock puppets. Only in Game Of Thrones they somehow mould it and turn it into the medieval equivalent of a bulletproof vest. It's not so much about staying warm, then, as staying alive .

In a recent lecture at New York's Metropolitan Museum of Art, Games Of Thrones costume guru Michele Clapton talked about the armour used in the HBO TV series. She revealed that, yes, the leather is moulded though she didn't reveal if it is actually boiled first. In other interviews she had said that one Games Of Thrones costume was inspired by the Alexander McQueen "bell dress" Bjork wore in her Who Is It? video and that she often turns to fashion for inspiration.

But as much as she borrows from fashion, so does it borrow from Game Of Thrones. A recent Helmut Lang Fall collection, for instance, featured something that looked suspiciously like boiled leather. Uh-oh.

Back in the real world, winter isn't coming and neither is there a rampaging army of barbarians bearing down on us from the south. Well, there's the Edinburgh Festival to endure, I suppose, but that's not quite the same thing. In other words I have more need of fresh cotton than boiled leather, whatever the fashion designer might think. Particularly when it comes to my "smallclothes".