Dave, all those pictures are more confusing, there are no dims showing thickness or even openings. The spanner my brother gave me would probably work if it was possible to get the spanner deeper, however the brass nut is almost touching the bottom of the main body of the Water Pump. This means the spanner has to be very accurate in dimension to pick up the slots in the nut before reaching the pump body on the opposite side.
Thanks for your research.
Davy
David Selfridge