One of today's leading news items is the UK Government's submission to the Calman Commission, the body looking at the allocation of powers between the UK and devolved Scottish Governments.

The thrust of the lengthy submission appears to be that no further significant powers should be devolved, and that there is a case for preventing devolved powers from being used to "undermine the delivery of reserved policies" - a reference to the threat to use devolved planning laws to prevent the building in Scotland of new nuclear power stations, something London ministers are keen on as a UK policy.

One wonders whether this is just an attempted show of strength rather than a move that is likely to be carried through into legislation, or in any event into practice if enacted. It would surely be entirely counterproductive in terms of popular sentiment for London to attempt to impose its will by overriding to that extent the policies of an elected Scottish administration of a different political hue. What would be the political consequences of Westminster forcing through the building of a nuclear power station in Scotland, against majority parliamentary and popular opinion in Scotland?

In the first years of the Scottish Parliament there was frequent use of "Sewel motions", under which Holyrood could resolve that bills which overlapped devolved and reserved powers be considered principally at Westminster. At one stage indeed there was criticism of their overuse, but it seems a long time now since we heard of them. Perhaps if Scotland cannot be persuaded to co-operate to that extent, London should accept that the reality of devolution requires it to work within certain limits.