Just to close this one off - I asked Fishbase if they had an expert to whom they could refer this ID . The photos have now been seen by Dr Jeff Williams in the US and Wouter Holleman in Zambia. Both have advised it is not E. mirabilis but E. tutuilae, the High-hat Triplefin. They say that the whitish first dorsal and the white bands on the other two dorsals running onto the body are diagnostic. Apparently it is a complex species with versions present in the Red Sea, west Indian Ocean, Gt. Barrier Reef, as well as Indonesia. Further work is needed to clarify and sort them out.
Thanks again Bart