JN
P-8 MAY have been selected without an exhaustive enough evaluation of alternatives, and especially of cheaper alternatives
What makes you think they weren't? Surely though, the most important thing is/was do they meet your requirement?
If the MoD direction was MOTS/COTS; what would the impact be on "paper" aircraft? Would a paper aircraft meet the "time" part of Performance/Cost/Time?
that the P-8 would not be an even better (and more cost-effective and value-for-money) solution were it to be able to use existing UK sonobuoy stocks ... and by being able to use the apparently highly regarded StingRay torpedo
Possibly true, but then you have to factor in the cost of integrating new launchhers, buoys and weapons onto a platform; how much does it cost to carry out the software mods, test them, complete separation trials and clear a weapon/system onto a military aircraft? How long has it taken to get new weapons onto Typhoon? Lots of software there, so I guess it won't be cheap. Then of course you are potentially operating a bespoke fleet that differs from your key Allies also operating the P-8; how does that impact upon through-life costs?
Of course the original SAAB Swordfish, particularly when the UK started their programme was a twin-turboprop, not a twin-jet.
Finally, be careful of senior officers pushing their own agendas; some aren't the best informed.