The Nimrod did carry nuclear depth bombs - up until about 1992 when they were withdrawn from service. As far as finding nuclear submarines goes, the Nimrod MR2 with its highly trained and experienced crews had a much better track record that our US allies at locating and successfully tracking Russian submarines. The airframe was old, but the kit on board wasn't. The gap in our defences and capabilities caused by the hasty cancellation of the MRA4 is yawning and humiliating.