David Cameron begins to make the emotional case for keeping Scotland in the UK

You may have seen the pictures of David Cameron chatting to some very small ponies on Shetland and, if you have, you may wonder, given what else he has in his in tray just now, what on earth he was doing there.

But the truth is there are few more important issues than the potential break-up of the United Kingdom and Mr Cameron certainly doesn't want to go down in history as the Prime Minister who presided over its demise.

David Cameron strokes a small Shetland pony.

Shetland is an interesting place, made relatively wealthy by oil and not all that interested in swapping rule from London for rule from Edinburgh. So he was making a point by going there in the first place.

In the interview I did with him, he stuck to his guns on the currency, insisting it was right to say the Scots would have to drop the pound, but it was evident throughout the trip that he was trying to make more positive arguments than we have perhaps grown used to in this debate.

I think he feels he has made the intellectual case for staying together, now he wants to make the emotional one.