1453Flt Neptunes
Beagle you were right the four Neptunes on 1453Flt were not MPA, however, they were not used for anything clandestine either.
They were conducting AEW trials from Jan 53 to Jun 56, I have been to Kew and have their trials report and version of the Fm540. Both make very interesting reading and their results are one of the main reasons that we didn't get an RAF overland AEW capabilty until 1972! Now there's a capability gap for you!
Ian