The Heading Reference System was, I believe, another spin off.
The HRS used two Master Reference Gyros, MRG, that were used in the F6 to give attitude information and translated in the Vulcan to give azimuth information. The accuracy was IRO 0.25 deg per hour and well up with conventional INs of the time and a lot better than some, like the Nimrod.
I believe components of the HRS were part of the Blue Steel guidance package whose IN only had to run free for a few minutes. I think that was the basis of the IN package for the Nimrod.
What goes round goes round.