It is often said that devolution is a process rather than a settled state and doling out additional powers piecemeal seems to increase the pressure for yet more.
Furthermore, this latest scheme is already under attack – from Mr Cameron’s own party – with the stated intention of legislation to restrict the voting rights of MPs from constituencies outwith England. This would mean that sometimes the Westminster assembly was, in effect, the English Parliament and, at other times, the UK Parliament. It could get even messier. Under our parliamentary system the party of government is the one which can command a majority in the Commons and it is quite conceivable that different parties would have it depending on whether all MPs could vote or only “English” ones.
The solution might well be to move to a formal federal system. If carefully framed it would probably not please many but still command wide enough acceptance, however grudging, to give it the measure of permanence many desire.