Came across this and various other related articles:
https://ukdefencejournal.org.uk/dron...avy-test-ship/
The rotary wing UAV used in this demo is apparently the Rotron Talon DT-300. I wasn't able to easily find an on-line data sheet for it, but it is likely powered by a pair(?) of Rotron rotary petrol engines driving its tandem rotors. The rotors seem sufficiently separated that there is no need for intermeshing rotors. So this VTOL UAV seems like a simple and efficient arrangement with far greater endurance than any battery powered VTOL UAV can offer.
One photo on Rotron website seems to also show a variant of it with a thruster prop at one end, and the quad legs retracted.