Yeah whilst at face value fitting Searchwater2000 and Cerberus might appear to be the cheapest quickest solution it might not actually be the case. At first they offered a palletised solution running off the back of a Merlin converted with a ramp, they are now offering a side mounted trapeze solution. Now when it was the idea that the spare HM1 not being converted to HM2 would be used it was not a bad solution but it appears the RN wants to use the HM2 with any airframe being used. Mounting the trapeze, pulling out the consoles to push in the Cerberus fit is a pain. On the other hand Vigilance hangs the radar pods off the HM2 torpedo rails and uses the already installed consoles with updated mission software. That offers significant cost savings and training advantages, it allows any airframe to be adapted to role quickly and a few extra training modules for those personnel who will man them rather then an entirely separate training stream for a unique AEW solution. It is also significantly more exportable albeit the Americans will mainly benefit from that.