It was a completely revised arrangement, as I'm aware, and had taken account of the concerns with the B1. As can been seen the a/c was a much revised airframe. I'm sure there are more informed minds on here who might be able to enlighten further.
On the B1 fatigue problem one a/c (XD816) was reworked completely by Vickers and a RTW campaign offerred to the Ministry, but they choose to withdraw the fleet having Victor and Vulcan coming on stream - more's the pity.
PFR.
The attached thread was running on PPRuNe some years ago - as always interesting reading, anyone care to add to it?
http://www.pprune.org/military-aircr...valiant-3.html