“[18] … the jurisdiction created bys 31(1) of the Matrimonial Causes Act 1973 (below) not only empowers the court to re-timetable/adjust the amounts of individual instalments, but also to vary, suspend or discharge the principal sum itself, provided always that this latter power is used particularly sparingly, given the importance of finality in matters of capital provision. “[57] Nevertheless, given the constant emphasis in the authorities generally on the need to uphold the finality of orders intended to be final, including orders as to capital, it seems to me that very similar considerations ought in practice to be appliedunder s 31 as those laid down in Barder v Caluori … any rate as regards varying theoverall quantum of a lump sum order by instalments (as distinct from re-timing or 'recalibrating' the instalments). [58] The re-opening under s 31 of the overall quantum of lump sum orders by instalments, especially when made as part of a package intended to be final (and all the more so when ordered by consent following an agreement) should only becountenanced when the anticipated circumstances have changed very significantly,and/or for cogent reasons rendering it quite unjust or impracticable to hold the payerto the overall quantum of the order originally made. [59] This formulation gives a little more latitude as regardss 31 of the Matrimonial Causes Act 1973 than do the Barder conditions for the grant of leave to appeal out of time; but that must I think follow from the statutory requirement under s 31(7) that the court is to consider 'all the circumstances'.”