Rual took a detour via Ayer's Rock (Australian joke -- look at Rual's photo to get it).
Jim, careful not to force any nut you buy at the local hardware store onto your Brooks saddle threads. They ain't heard of metric yet, and it might not even be a standard current British thread, instead being Whitworth, very common until after the war.
Trivia: I won't have any trouble undoing the first series Rohloff sprocket because I still have a hew-huge Whitworth wrench I have left over from my Bentley days which is the precise equivalent of the metric Rohloff sprocket socket.