All the info on RIVET JOINT and the HELIX Program you need is here:
RAF Rivet Joint ? How Much? | Think Defence
If you can't be arsed to read it then I will spell out the headlines:
As the MRA4 programme progressed a replacement for the MR2 era R1 was being though about (via Project HELIX) and various suggestion surfaced including the RC-135 Rivet Joint, an upgrade of the existing aircraft, a version of the MRA4 or some other completely new aircraft.
RIVET JOINT selected.
R1 withdrawn in 2011 and UK RIVET JOINTs will deliver in 2014. To guard against skills fade the RAF crew will enter into a partnering agreement with the USAF.
Money wise, the post states "the US Defense Security Cooperation Agency published a notification of a possible sale to the UK of three RC135 RIVET JOINTs and associated support and logistics systems for up to $1.068 billion"
So 3 aircraft will cost us approx £690M (assuming $1.55 to £1) - I agree with the author of the article "In all fairness it is not a bad deal, the alternative in these budget constrained times is nothing".
I do disagree with the author on RIVET JOINTs capability vs Nimrod R1 - having received a service from both in the past it was hard to tell the difference (apart from the Texan drawl!).
Thank God we're not giving t'bunglin baron waste-o-space a shed load of cash for Nimrod R5 to deliver probably in 2025 (if we're lucky)!
LJ