Regardless of the outcome of the referendum campaign, I fervently hope the energy, enthusiasm, and commitment to change the political landscape will not fade away.

Inevitably there will be disappointment and tears. There always is in politics. But now, since some people have found out, perhaps for the first time in their lives, that politics can change the world, I hope they maintain their zeal.

I will be sad if Scotland breaks apart from the United Kingdom. I was born in Glencoe, I was brought up in the Highlands, and I've lived and worked near London. I don't look forward to anybody in the UK being able to say I'm a foreigner.

I completely understand why people feel alienated from the political process and why they want it to change. But I know that sentiment prevails throughout the UK, and is as relevant in Brixton and Birmingham as it is in Bathgate or on the Butt of Lewis.

I want the political structures to change so people throughout the UK feel engaged, to know that their voice counts, that they can make the differences they want to their daily lives. And that can be done without risking our security and opportunity.

The cost of setting up a separate state will be immense; that is always the case with democracy but that will be the least of it. Voters in Scotland are being asked to take a leap into the unknown but only up to a point.

They can at least be certain about uncertainty because, with only hours to go before the result is known, the two-year campaign trail is littered with unanswered questions.

No less than Professor Ronald MacDonald, the estimable economist, warns of years of austerity if Scotland decides to separate from the UK. The reasons are not complicated. In Glasgow, on Monday night, you could almost hear reality dawning when Professor MacDonald explained the pound did not belong to Scotland, England, Wales or Northern Ireland.

Rather, it belonged to the UK and, if Scotland or even England left the UK, then they would leave the pound. It is as simple as that. And it is worth noting that any currency option, apart from the one we enjoy at present, will be expensive and will be paid for by draconian cuts in public services or huge tax hikes. There is no alternative.

Experts say we will not automatically join the European Union. There will be no seamless transition; it could take many years; and there is no guarantee that the UK's hard-won opt-outs - not being in the Euro, no EU control over national budgets, the UK rebate, control over borders and VAT exemptions on everyday goods - will be transferred to Scotland.

I don't agree with Nicola Sturgeon, the Deputy First Minister, who says the ties that bind the countries within the UK are about people not politics. Certainly, people are important but, whether on the left or the right, ideology transcends borders and has done since time immemorial; and not merely within the UK but around the world.

In the 18th century the Scottish Enlightenment gave the world the idea of a civil society and, after the Industrial Revolution, Scots led the way to a 20th-century citizenship that guaranteed social and economic as well as civil and political rights. In the 20th century, Scots along with the English, the Welsh and the Northern Irish, faced down fascism in the Second World War, standing alone for many months.

In the second half of the 20th century they worked together to build the NHS and to introduce progressive policies, whether womens' right, devolution or the minimum wage.

The strength of the UK enabled Scotland to withstand the disastrous consequences of the global financial crash. Without the broad shoulders of the UK, Scotland would have suffered the same fate as Ireland and Iceland.

On Tuesday night President Bill Clinton urged Scotland to send a powerful message around the world, to show it's possible to respect differences while living and working together. In a world torn by identity conflicts it is the greatest challenge of our time, he said. Scotland has the chance to show the world it can be done.