Gordon Brown was the last Scottish Prime Minister of the UK. Ever. Even if we do not win independence in 2014 there will never be another Scottish PM of the UK. It is inconceivable that an MP representing a Scottish constituency could lead a UK Government which mostly legislates on matters which do not effect Scotland. It is highly unlikely that someone perceived to be a Scot, even if they represented an English constituency, could aspire to the office.

Our current Devolution settlement already makes this impossible. It is only a matter of time before Scottish constituency MPs are restricted on what they can vote on at Westminster. Scotland clearly needs and desires at least greater autonomy, and the Unionist parties are saying it will be delivered if we vote No.

So what is Jim Murphy‘s ambition? What are the ambitions of Scots unionists?

It is probably unfair to pick on Jim Murphy but he is clearly an eloquent and skilled Labour politician. He sits in a cabinet of limited talent with a leader who lacks credibility. Yet he cannot aspire to much beyond Defence Secretary in a future Labour or coalition Government. He could possibly aim for Foreign Affairs, but not Health, Education or the Environment. Possibly he could fill a minor financial role but certainly not Chancellor of the Exchequer.

Scottish unionist politicians do not seem to have caught up with this fact. After the London media’s anti-Scottish campaign against Gordon Brown their colleagues on the green benches understand the new reality in England. This week a bizarre article in The Scotsman from Liberal Democrat MSP Tavish Scott complained that the best Labour talent has sought Westminster rather than Holyrood. It is an old complaint, much repeated, although it resonates with the echo of Smith, Brown, Cook and maybe Darling, more than with the current generation. Scottish Labour’s Westminster tribunes do retain a high sense of self worth but their path to advancement is severely limited.

And whatever the sentiment of the London media the reality is that the UK constitution is no longer fit for purpose. Scottish MPs voting on English Education or Health is unsustainable. Whatever Scotland’s choices, it does not work for England. And rightly so.

The latest exercise in delusion are the proposals for reform of the House of Lords. This is portrayed in the media as the pet project of the Liberal Democrats. They are supposed to be in favour of federalism for the UK, which does have the advantage of logical coherence if not popular support. But there is no hint of federalism in their proposals for the UK’s second chamber. Or indeed of any acknowledgement of the diverse political reality which encompasses the Welsh Assembly, Stormont, Holyrood and a House of Commons that makes laws for England with 117 MPs from non-English constituencies.

The UK non-constitution is no longer fit for purpose. It is not just that Scotland would be better off with independence. The current system does not work for Scotland or the other parts of the UK. If we vote No in 2014 we can look forward to a future of increasing marginalisation in London and growing mutual resentment. Believe unionists promises on increased autonomy if you like, but they have not even begun to think through what it means at UK level. And funnily enough, it is a waste of Jim Murphy.