There are two things which are striking about British culture.

Firstly, our rich and extraordinary history. Secondly, our often breezy complacency in the face of it.

This lightly-held sense of ourselves - our humour and tolerance - is one of the reasons why I love Britain. But we need to guard against insouciance descending into neglect. The SNP is telling another story - that the end of Britain is inevitable. If all unionists offer in response is a tolerant shrug, then the SNP's version of history will become self-fulfilling. The union could easily end not because of deep divisions but a sheer lack of thought.

For those reasons, as a Scottish Unionist, I was delighted that David Cameron used his first speech after the Conservative's victory in May's election to spell out his plan to "bring our country together". It is now vital we follow through on that ambition.

We do it first devolving substantial new powers to Scotland and Wales, as promised. The new Conservative government has already made this a priority. It will do much to bring about a fairer settlement across the UK. Much of Scottish spending will soon be met by Scottish taxes. Within the union, Scotland will have a parliament which, rightly, takes far more responsibility for its own spending decisions. This is as it should be.

But this is only part of the reform the country needs. We are a nation which spends millions on diplomatic relations with foreign states. Yet we spend remarkably little attention on the internal functions of our own state. Devolution has created new centres of power across Britain. This government's plan to drive power down to England's great cities will extend that trend further. In the face of this, we need to give more thought to how solidarity and autonomy operate together.

That requires stronger inter-government working arrangements between Whitehall and the devolved administration and regions. When Labour set up the Scottish Parliament it seemed to assume that everything could be sorted out with the odd phone call between party colleagues in London and Edinburgh. The UK government is now acting to improve that with a much clearer set of guidelines.

It means an understanding within Whitehall and our devolved capitals and regions that they are in a power-sharing arrangement and must therefore work in harness. And a family of nations will only succeed if it maintains a conversation. So, for example, one suggestion the Scottish Conservatives have made is that representatives of all the Parliaments and Assemblies of the Union meet regularly on a formal basis to examine their respective roles. This would be a forum where the moving parts of our new Union could be seen in the round. We should not work separately from one another; a healthy Union is one which continually seeks to learn from its different constituent parts, and simply keeps talking.

These are just some ideas but they point towards what is required: not just more devolution, but also more union. Devolved institutions have sprouted up across the UK in the last two decades. We now need institutions of the union to catch up.

Britain has always worn its constitution lightly, not least in refusing to follow the fashion of the 1700s to the present day in codifying itself in a single document. But that laissez fairer approach should not hide the reality of what we have built together - the greatest political union in history. If we want to keep that Union together, then it is time for the Union to act.