Help please! Memory and photo album have failed me here

.....in my store of dismantled bits I found this piece of angled ali sheet today. Must be some kind of mud or heat shield (it was lurking in a box marked "RHS mudshield etc", if that helps. Duh. Painted black and somewhat oily, about 28 cm long. Can't see it in Parts catalogue or Factory Fit. (Mine being a late S1 it wouldn't be the only S2 component fitted that isn't in the book.) Any suggestions where it came from? Thanks!
