IN a sense, we could be described as the political odd couple.

One of us is a diehard Liberal Democrat and the other is Labour to his very bones

There are several policy areas where, respectfully, we agree to differ. We don't even see eye-to-eye about football.

On one fundamentally important level, however, you cannot put a cigarette paper between us. We will always do, always fight for, what we believe to be right for Scotland.

In the 1980s and 90s, we campaigned shoulder-to-shoulder against the Poll Tax and for Home Rule for Scotland.

We then sat, with other like-minded reformers from Scottish civic society, on the Constitutional Convention, creating a template for a strong Scottish Parliament with real powers, inside the UK, making the right decisions for Scotland.

In 1997, we had the pleasure of campaigning together and winning a Yes-Yes vote in what was the most successful UK referendum result ever.

Two years later, we welcomed each other to Parliament and to the first Scottish Cabinet, a historic day, that we remember, 15 years on, in a very different Scotland, one that that Parliament and its MSPs have helped to forge, with the people of Scotland, for the people of Scotland.

Think back to what actually has been changed by Holyrood in that decade and a half.

In fact, to borrow from another classic film, let's have a "what has the Scottish Parliament ever done for us ?" moment.

We led the way on the smoking ban, a piece of legislation taken as common sense now but deeply controversial at the time: land reform; free personal care for the elderly; free dental and eye checks; the abolition of tuition fees; changes to the justice system; and equal marriage legislation.

We could go on but, the point is, devolution allowed us to make fundamental changes to the way we live in Scotland while sharing decision-making with the rest of the UK, where it makes sense. Have the last 15 years been flawless?

No, but, as the slogan says, we're better together, not perfect together and that is why we believe those who would break Scotland apart from the rest of the UK are offering a false choice.

The devolution process was never meant to be set in aspic and it never will be.

From the very outset, the settlement has shown itself to be flexible and dynamic.

Additional powers were devolved to ministers that enabled the development of Scotland's renewable energy resources.

Later, there was devolution of responsibility for rail development, which led to the opening of new routes.

This year, the settlement was amended to facilitate the establishment of a new Food Standards Agency for Scotland.

Most significantly, and ahead of what is promised by each of the three main parties at Westminster, the Scotland Act 2012 already includes significant new tax-raising powers.

In short, we have a system that retains all of the benefits and security of being part of the wider UK but that has also proved readily adaptable to Scotland's changing needs.

We worked most closely together between 2001/05, during our spell as Deputy First Minister and First Minister.

We had our ups and downs but, more often than not, we found that, working together, we achieved far more than when we sought to create artificial dividing lines.

We are united again in the campaign to keep a vibrant Scotland part of a flourishing United Kingdom.

This is not because of our political allegiances or prejudices but simply because we passionately believe with our minds, and our hearts, that not only is it the positive thing to do, but also that it is the right thing to do.