Is the chance of an air launched system once again, as has been mooted, at all viable does anyone think?
Launched from what???
And I don't meant to be facetious in saying that. But we are shedding airframes at a worryingly rapid rate, and apart from having the platform to actually hang it off, I'm not convinced the associated infrastructure both physical on stations and enabling patforms exists. How many airframes did it take to keep a nuclear Q going before we handed the responsibility to the RN? How many B-52s did the USAF require to keep their airborne nuclear alert going during the height of the Cold War?
And then the costs of converting to an air launched system and integrating it on a platform would no doubt not meet with treasury approval in these straightened times. You might get away with converting Storm Shadow or adding to the TLAM fleet with air launched nuclear tipped, but again it's down to costs. I hate to say it but for now, I think this one will stay with the RN on the grounds of at least its a proven capability and (relatively) known costs.