David Cameron and Nicola Sturgeon's meeting in Edinburgh delivered more in the way of answers than many were expecting.

We learned, first and foremost, that the Prime Minister will listen to arguments from Scotland's first minister about extending the scope of the draft devolution bill.

He had appeared, previously, to suggest that the existing plans for implementing the Smith Commission's report on greater powers for Holyrood were sufficient. But after meeting with Ms Sturgeon he seemed to concede that the draft bill does not go far enough, declaring himself willing to 'beef it up'.

The Holyrood Devolution (further powers) Committee's recent verdict that the bill falls well short of the agreements set out in the Smith Commission proposals, drew particular attention to welfare, for example the exclusion of the commission's aspirations that Scotland's government should be able to introduce new benefits or top up existing ones.

This will be looked at, but Mr Cameron went further, saying other powers - beyond Smith - could allow Scotland almost complete control over income tax, air passenger duty and housing benefit. He also pledged regular meetings with Ms Sturgeon.

It is all a far cry from what some feared - that Mr Cameron, reinforced by the election of a majority Conservative government would deliver new powers only under the existing terms of the bill.

Nor is it the approach suggested by some, including some in the Conservatives, that he would give the SNP what they have demanded in terms of full fiscal autonomy - on the assumption that a potentially large budget deficit and the need to implement austerity measures would burst the party's bubble.

In truth it is not a surprise, but certainly welcome that Mr Cameron has chosen not to pursue some of the wilder scenarios which had been posited. If the union is to survive - his desired outcome - he must steer, and must continue to steer, a course which acknowledges the scale of political change under way in Scotland. Despite the pre-election posturing over Scotland, he now seems to be taking seriously the historic voting shift in Scotland and its impact.

Ms Sturgeon acknowledged that the meeting was positive and that other areas in which she will be pushing for more control include business taxes, employment law and the minimum wage.

However there are red lines for Mr Cameron, who is not willing to contemplate the SNP's desired full fiscal autonomy. The Conservative leader insisted Westminster can and will abolish the Human Rights Act for Scotland. He has also ruled out a veto for Scotland, should the EU referendum result in a vote to leave.

This raises massive questions. The government can repeal the human rights act for Scotland as well as England, but cannot straightforwardly replace it with its proposed bill of rights. But this is perhaps an opportunity for Ms Sturgeon to bring forward legislation at Holyrood to help deliver and crucially embed human rights in Scottish law.

More problematic is Mr Cameron's understandable insistence that an EU referendum vote would be binding on all parts of the UK. His position is understandable, but the political reality quite different.

It is unthinkable that, in a scenario where Scots had voted to stay in the EU and the rest of the UK opted to leave, the UK government could simply say Scotland's view did not matter.

In his readiness to enter talks with the SNP leader, the prime minister shows a welcome understanding of the need to address the fact that Scotland's voters chose something quite different from what they have ended up with.

If the same principle did not apply to the EU referendum, calls for a further referendum on independence would be very hard to ignore.