Mine does the nut on a 40mm McAlpine plastic multifit compression fitting, so I doubt that it's too small Chris.Softus - I don't think that jaw will do inch and a half, it's too big. There's a gap in the scope.
However, I bought it specifically for undoing the traps under shower trays, so it might not be man enough for a 28mm/1" brass fitting, but the tool copes with some tough b*ggers of sink tap backnuts.
Anyway, since I posted that image we've seen the extent of the OP's non-problem, which is solved by a few minutes of firkling, as you and Paul rightly pointed out.