The current S of S is a career politician and as such knows very little about defence and must rely on being briefed by those who should know more but often don’t. He will be doing a different job in a few years (or months) anyway so let’s just forgive him his rather limited knowledge.
The current CAS is a former Tactical Reconnaissance pilot and as such ought to have an understanding of surveillance (albeit dated) and not related to the Maritime role.
Given this it is easy to see why he is such a fan of ‘Scrimager’ as he calls it and UAV’s (sorry Steve RPAS) in general.
If the MPA job was simply surveillance then it is just possible that in some circumstances an RPV could do the job. But an MPA is much more than that, take a look at all the other countries that operate them and see what they do.
RPV based surveillance could well complement the space based Ship Plot style systems to detect and perhaps identify surface targets – then what?