The Labour government’s plans are closely based on the findings of the Calman Commission review of devolution, with most of that commission’s proposals accepted.

Accountability for spending taxpayers’ money in Scotland would be paired with accountability for raising it, Mr Murphy said, with Holyrood awarded new tax-raising powers.

Other Calman recommendations are set out in the government’s white paper, including new borrowing powers for the Scottish Government.

But the borrowing powers are hedged with caveats. Any Scottish Government planning to use them first would have to seek approval from the Treasury, and would have to repay any sum borrowed by raising taxes.

Powers to change drink-drive limits and speed limits are highly unlikely to be used. Even the power to ban air guns is initially useless until a definition of what constitutes an air weapon can be agreed.

For the UK Government, the message is a simple one about accountability. Scotland’s devolved administration can have more powers, but at the price of greater fiscal responsibility. Blaming London for the nation’s ills no longer will be credible.

The SNP doesn’t accept this, and views both the tax-raising and borrowing powers as deeply flawed.

But nothing more will happen to the Labour government’s proposals before next year’s General Election. A Bill after the vote, with a transfer of powers by April 2012 at the earliest, and possibly not until 2015, is the most Mr Murphy is promising. But what will happen if, as looks more than likely, Labour is not in power after Britain goes to the polls next year?

Well, we’ve learned that the Conservatives would also accept most of the Calman proposals, in principle. But they would not be a priority and the Tories presumably would face the same barriers to early delivery cited by the Labour government: a need for robust transitional arrangements and a degree of economic stability before change can be advanced.

All of this works primarily to the advantage of the Nationalist cause in Scotland, with the SNP able to portray its opponents as delivering nothing but promises of jam tomorrow.

The perceived inability of the Scottish Secretary -- or, indeed, any of the Unionist parties -- to deliver for Scotland, and the future of the devolution settlement will become a key election issue north of the border next year, in a way that plays right into the hands of Alex Salmond.

Mr Murphy’s goal in revising the devolution arrangements was to settle the issue for a generation or more. That now looks like an impossibly high ambition for the current white paper, which is unfortunate, to say the least, for the cause of Unionists of all political persuasions.