After having an interesting chat with people at North Weald, I have learnt that for the undercarriage systems to be operable on a Piper Navajo at least one of the engines must be operating, and N80HF landed gear-up on the 25th July 2010. Of course, the undercarriage could be deployed using the emergency extension procedure for that aircraft, although I can imagine that might be quite difficult whilst dealing with a double engine failure.
From one look at the aircraft (it's sitting outside at the Squadron) you can tell that it has clearly had a gear-up landing, although interestingly on both propellors two of the blades are damaged with the third being untouched, and there is no obvious deformation of the shape of the blades to suggest that they were under power at the time of impact. Correct me if I am wrong but I believe that the only situation that can cause both engines to fail simultaneously is a lack of fuel. How very interesting.
Thank you for those who have PM'd me so far, but if anyone does have more information or a witness account of this forced landing it would be very much appreiciated.
Kind regards,
Ox