can anyone explain the basis of the £ 4 Bn per year please?
The AFPS has stated:-
"In line with other public service pension schemes the AFPS has considered the potential impact on the outcome on the scheme and, as a result, felt it prudent to increase the past service costs. For the AFPS this has been estimated at £1.9 billion and has been recognised in 2018-19. Further details on the valuation of the liability, the key assumptions and uncertainties can be found in notes 2.1 and 13.4 to the accounts."