Thanks for the comments.
Bluelion,
Ah! The wonderful world or defence procurement.
The decisions made are strange at the best of times but add in a country that no longer can afford the kit they have ordered you get some very strange decisions.
To be fair to them, it can't be easy. A defence procurement will have to meet the needs of the MoD, the budget of the government, predict what the requirements will be in the future (no one has ever managed that!), the political aims of the party in power (that party may change several times in the life of the project) and also to make sure that as many British jobs are supported as possible.
The Nimrod both R1 and MR2 didn't recover from the political fallout from the loss of XV230 and 14 servicemen in Afghanistan. The MRA4 and Rivet Joint were rushed in to replace both types but with no cash left to fund it they delayed the introduction date and cut numbers. The cost of not operating the MR2 between now and the introduction of the MRA4 will save some cash in terms of running cost and not having to perform deep maintenance on some of the airframes. The MRA4s that aren't used, I suspect, will be broken down into parts for spares.
It's not good news and each branch of the military has suffered in some way or another but thanks to Labour committing us to Iraq and Afghanistan and thinking they can get away without increasing the defence budget it is the reality we find ourselves in.
Hopefully the next government won't be so stupid.