This is very bad news indeed, especially if it turns out to have been shot down. The Nimrod MR-2 fleet has been increasingly in demand in the last few years for very different roles to its primary mission, patrolling the North Atlantic looking for submarines and the shipwrecked, as the Army has become aware of some of its capabilities - a huge range of radio communications, excellent IR and radar surveillance, and more besides. Not only the Nimrod, but also the Royal Navy's Sea King ASaC-7 early warning helicopters, have been drawn on for overland ISTAR (Intelligence, Surveillance, Target Acquisition and Reconnaissance) tasks - both have the Searchwater 2000 radar, originally developed for spotting ships but also suited to spotting tanks and even aircraft.
This is problematic, as the plane itself is not really suited for this role. The operational pattern is essentially flying around slowly at 500 feet or so, as over the North Atlantic, whilst the electronics team investigate suspicious goats on request from the army. This is not ideal, especially not for an aircraft with a crew of 14, no armament of any use over land, and the performance of the 1950s airliner it is based on. Especially not, either, when the upgraded MRA-4 programme has been such a cash-guzzling disaster flick and only 12 of the planes exist. (The position with the even-fancier electronic intelligence spy ship, the Nimrod R-1, is even tighter - the total fleet is 3.)
A broader point is that there has been a lot of faith in the last few years that "platforms are irrelevant" and only capabilities count. Hence it's fine, indeed very wise, to use a maritime patrol aircraft over a hostile land battle at low altitude because it has the sensors you want. It's cheap, after all. This only works, however, if the enemy are clueless enough not to shoot at the big grey bird chugging about in the weeds. Perhaps they were five years ago, but learning in wartime is Darwinian.
Another point is that wars strain non-obvious capabilities. The Government has always been keen on cutting "nice to have" or "non-core" activities in favour of "the front line" - perhaps more so in the last few years with the advent of the consultant raj and their obsession with the core business. But this only makes sense if you know what "the front line" is. The Nimrod crews - the Kipper Fleet - and the RAF air transport fleet have been the hardest-worked and most-risked segment of the force, whilst the fighter/bomber force mostly defends the Norfolk coast. The photo-reconnaissance force has been under even greater pressure, and has seen its aircraft (the Canberra PR-9) withdrawn in favour of an as-yet undelivered converted business jet for its pains.