NHS job re-evaluation

[WhatGoesUp]

I work for the NHS and my job was put in for re-evaluation due to me taking on extra responsibilities. The process dragged on and during that time I decided to move on so handed in my notice. Following my departure the role was successfully rebanded to a higher grade and the now vacant post was advertised as such.
My question is, although I am no longer working there, should I be entitled to back pay from when I took on the extra responsibilities until I left?
At what point does the rebanding apply? Is it from when you take on the extra work or from when the re-evaluation is successful?

Check with HR but my guess would be when it went to the variation board and the higher banding secured within the budget. It's highly unlikely you are entitled to any backpay unless it's been agreed with your manager.

This happened to somebody I work with she stayed in post, but got her pay from when they agreed the higher band, no back pay.