In the past I often referred to NYIF cable, now I found a pic of it.



It's about my favourite type of cable because it's easier to install in old plaster walls than NYM. The price is rather hefty, 79 ct/m compared to 59 ct for NYM at Conrad Electronics and about 18ct/m at most hardware stores.
As you can see it'S very flat and hence perfect to install in walls or ceilings with very thin plaster (e.g. concrete ceilings). Most of all you can just drive nails between the conductors to secure it, and I don't mean tiny toy nails. I've used 70mm nails in walls with crumbly mortar between the bricks. It's lsited for use in all domestic and (I believe) commercial environments but not in agricultural structures, and it's only listed for use in plaster and brick/concrete/... walls, not in any wood structures. That is because the outer sheathing is pretty thin compared to any other type of cable. NYIF used to be very common in the 1950ies to 80ies, then NYM almost killed it in Austria, along with conduit (PVC flex) that has always been very popular here. In Germany there are still many electricians who prefer NYIF. The last time I wanted to buy some the electrician asked me: "_What_ do you want? _No one_ buys that any more!". Then she went to the back of the shop, returned with a huge coil of the cable and started unraveling the 10m I had ordered. While doing that she almost tripped over the loops of cable on the floor several times, almost if she were doing some weird dance... the fun was almost woth the extra price!

Wouldn't you have to be very careful not to contact the conductors if fixing this to walls with nails through the insulation?

I fully appreciate that being so flat this cable seems ideal for those places where there is only a thin layer of plaster (too many of those solid brick walls in Britain as well!), but I wouldn't want it sitting that close to the surface without protection.

No, there's really much space between the conductors, so you have to be very stupid to hammer a nail right into a conductor. Though I've seen situations were even licensed electricians obviously managed to do so. There's a bout 2mm of room there, and the link between the conductors is very thin and soft, so you can easily pop thin nails through the link with your fingers and the hammer them into the wall.
AFAIK code calls for 4mm of plaster covering NYIF. Austrian NYIF is great, even when pretty old, but old German NYIF was notorious for getting hard and crackling away. All plasticiser out I guess. In theory I could leave that stuff anywhere I find it, in practice I tear it out anyway beacuse I can be pretty sure there are some illegal splices and taps hidden somewhere in the run. However, I've reused many pieces of NYIF with the old color coding. It's pretty handy if you're rewiring a place and run out of new cable and just find a scrap piece of old cable that's just a bit longer than what you need. For example i've wired our entire bathroom except for the receptacles with grey and black NYIF 2x 1.5 I tore out somewhere else in the apartment. Maybe it's not absolutely legal, but hey, the house is 90 years old, who the heck can prove that hasn't been there for ages?