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If Scotland gets the powers promised to it by the Smith commission, the consequences will be felt across the whole of the United Kingdom.

First, there will be increased demands for more devolution elsewhere.

Many English MPs will want a greater say at Westminster over legislation that only affects England. William Hague is chairing a cabinet committee to come up with plans to make this happen, plans that will be published in a few weeks' time.

There are also calls - from all sides - for greater devolution within England. The Chancellor, George Osborne, is already offering more control to what he calls the "power houses" of the north of England such as Manchester and Liverpool. A letter from Boris Johnson and other municipal leaders calls for "a comparable package of measures for local government in England".

Expectation raised

In Wales, too, assembly members want greater control over their affairs and already Stephen Crabb, the Welsh Secretary, is holding cross-party talks to discuss what this might entail.

And in Northern Ireland, Stormont is expecting to be given very soon - perhaps even next week - the power to vary corporation tax so it can compete with the Irish Republic.

But there are risks.

Some MPs believe that these demands for extra devolution outside Scotland will not - and cannot - be met in full. They fear expectations will be raised that cannot not be satisfied and this will fuel resentment towards Scotland.

Second, there are fears among some MPs and peers that piecemeal constitutional reform will have unforeseen consequences that could damage the union. Some argue, for example, that giving Scotland the power to set its own income tax will make it harder for a UK government to raise revenue and thus manage the economy. Borrowing costs may rise as the financial markets hedge against risks that should be shared by the UK as a whole. These critics - such as Gordon Brown and Alistair Darling - fear economic ties that bind the union together are being loosened to a dangerous extent.

Other MPs simply fear that English, Welsh and Northern Irish voters will resent Scotland being given so much in what some see as an unnecessary last-minute bribe to keep Scotland in the union. They worry that some UK voters will ask why Scotland is keeping the generous "Barnett" funding settlement that many think is unfair but which David Cameron made clear last week will not be changed.

Third, the biggest political impact will be felt by the Labour Party. They have no choice but to accept the Smith Commission. To do anything else would be a gift to the SNP, against whom Labour is struggling to compete.

But many Labour MPs fear the consequences of this will damage the party severely in the long term. They fear that giving Scotland income tax-raising powers will make it impossible for Scottish MPs at Westminster - most of whom are Labour - to vote on budgetary matters that affect the rest of the UK.

Trust in politics

This will fuel the argument that English MPs should get the right to vote on all English-only matters. And if that happens, Labour fears that it might struggle ever to form a government in the future if it has a majority in the UK but not in England.

In these circumstances, could a Scottish Labour MP be prime minister? The depression among Labour MPs over this cannot be over-emphasised. But for now the party believes it has no choice but to deal with the immediate problem of the SNP ahead of next May and ignore the longer term problems that English votes for English MPs might entail.

But perhaps the most significant consequence of the Smith Commission is over the question of trust in politics.

The promise that Mssrs Cameron, Miliband and Clegg made in the dying days of the referendum campaign was the most important political commitment of this parliament.

If there had been any sense that they were back-tracking on this commitment, then the impact on public trust in politics would have been incalculable.

Clearly there will be disagreement over the detail, and many Yes campaigners will wish that Smith had gone further. But fulfilling the so-called "vow" to give Scotland more powers will, at the very least, mean that Westminster does not suffer yet another loss of public trust that it can ill afford.