Some of those who will vote Yes on Thursday have been convinced believers in the cause for ages.

Others, such as myself, have had a more problematic and difficult journey. In the 1970s and through most of the 1980s I was hostile to the notion of Scottish independence.

I well remember the moment when I slowly began to have second thoughts. It was on the editorial floor of The Herald in the early spring of 1988. We were discussing the Budget, one of the great set pieces of the Westminster year.

A young SNP MP called Alex Salmond had disrupted the august occasion. He defied convention by interrupting the Budget speech of the Tory Chancellor, Nigel Lawson. He stood up and yelled that it was an "obscenity". Worse, he then defied the Deputy Speaker when he was told, in effect, to sit down and shut up.

Then he was "named". This meant that he had to be expelled from the Palace of Westminster. But first an emergency debate had to endorse the decision. So the Budget speech was well and truly wrecked.

My initial reaction was that Salmond was a truculent young whippersnapper. He had embarrassed himself and his tiny party. This was also the view of my editorial colleagues, most of whom were Labour voters. The editor, Arnold Kemp, told me he thought Mr Salmond had demeaned not just himself but Scotland. He felt ashamed.

Much later, in the pub that night, the same views were being repeated, with more venom. By now I was confused. Mrs Thatcher and Nigel Lawson and all they stood for were hated and reviled by these colleagues. Why was this hatred now suddenly turned on Mr Salmond? It didn't make sense.

My friends insisted that opposition was the job of Labour, then led by Neil Kinnock. I thought: Really? Who are you kidding, apart from yourselves?

Up till 1987 I'd been a conditional and lonely supporter of Mrs Thatcher. I realised after her third General Election victory that hubris had set in. She was out of control, and had lost touch with reality. She was a danger to sensible government.

Nigel Lawson's 1988 Budget was grievously irresponsible. It slashed taxes for the well-off and introduced the poll tax for Scotland ahead of the rest of the UK. It was financially as well as morally wrong. It was bound to fuel inflation (and indeed within a few months the inflation rate had doubled).

Mr Salmond's fury may have been planned but it was valid. The Budget was soon denounced by many, including some Tories. It emerged that even Mrs Thatcher herself reckoned that it was a mistake and that her Chancellor had set completely the wrong course. She lost all confidence in him.

So Mr Salmond was right. But the political mindset in Scotland at that time was naive and simple: Let Labour deal with the Tories. No matter how ineffective Neil Kinnock, the garrulous Opposition leader, was; no matter that Labour had just lost a third general election in a row.

I cannot claim that I suddenly saw the light. But I did know that Mr Salmond had been brave, morally and physically. He had faced down the baying, frenzied ranks of hundreds of MPs, puffed up with furious, self- serving indignation, on both sides of the House.

If anything, Labour MPs had been angrier than the Tories. Mr Salmond had shown composure and courage.

It took a long time for me to become a supporter of independence. But that night, mulling over the reaction to Mr Salmond's intervention, I understood that whether you were on the right or the left or even the good old middle, you could not really trust the two great parties, Labour and the Tories, to look after Scotland.

Support for the Tories soon collapsed in Scotland, but Labour - thanks mainly to the emergence of a cadre of fine politicians such as Gordon Brown, Donald Dewar, George Robertson, Robin Cook and John Reid - could claim to speak for Scotland, and the rise of the SNP was delayed. But only delayed.