Strange triangular screw head

[Fredxxx]

You obviously live in or close to Manchester?

[Bob Eager]

That's a Hampstead screwdriver.

[Dave Plowman (News)]

A bi-hex socket or ring spanner will grip it.

If you can measure the size of the triangle accurately might be possible to guess at which one.

[Ranger]

Yeah, that's certainly true of the bulk of small appliances that use them. And in a hole that is too small for the bigger nut drivers too, or too deep.

[Ranger]

That one doesn?t either. 2 sides are concave, one side convex.

Fifteen quid via eBay,

[Michael Chare]

Mole grips might undo it, if it is not recessed and there is access from the side. Stilson might also work.

[Thomas Prufer]

Find a piece of suitable aluminum tubing, and pound the tang of a triangular file down that to get the shape you want...?

Thomas Prufer