The two men vying to be the UK's next Prime Minister will go face-to-face for the first time in the Conservative leadership race tomorrow at 8pm on STV.

Many of the votes have already been cast, with ballot papers going out over the weekend, but we have yet to see just Jeremy Hunt and Boris Johnson square up to each other in a head-to-head debate. It's the kind of debate that lets us see what they are like under pressure and really tests each other's arguments.

On Friday night they were in Perth for the party's only Scottish leadership hustings. They wouldn't go face-to-face with each other, but they kind of went face-to-face with me.

I had never met either candidate before, and it was the first time I had interviewed them. Interviewing politicians in front of a live audience is very different from a TV studio or on some visit set up by government or party press officers. You get an instant reaction, which can be tricky for the politician and the interviewer.

At Perth Concert Hall there were 500 Conservative Party members gathered to see their next leader, the country's next Prime Minister and maybe even get the chance to ask him a question.

Many had already made up their minds, wearing 'Jeremy Hunt' stickers or 'Back Boris' badges.

Hunt had already spoken to a group of supporters across the road at the Royal George hotel. Borders MP John Lamont was manning a stall in the foyer with other serious looking supporters.

Aberdeen MP Ross Thomson was organising rowdier support for Johnson, gathering for group photos and cheering loudly when their man appeared to join them.

But then it was in to the hustings. Hunt was up first. He delivered his opening speech without notes (and without jacket, striding the stage a bit like David Cameron used to do), then took ten minutes of questions from me before facing the membership's questions. The key point I took from it all was that he would not devolve the powers for another independence under any circumstances. That got him loud cheers in the hall.

It was a fairly straightforward political interview, in that sometimes he went on a bit and sometimes I interrupted him and tried to hold him to account. He addressed the members questions on Brexit and business among other things very soberly and seriously, and they were very appreciative.

Johnson was next up. Delivering his opening speech from the lectern, I caught about half of it, the rest sounding a bit mumbly. Interviewing him is different, though. It is a bit like facing a steamroller head on.

The only way to get any questions in at all is to interrupt his stream of semi-consciousness. It's also a bit like herding cats, with more cats joining the herd all the time while others shoot out from every side. He goes off at tangents and sometimes seems like he is all over the place, which means the only way to try and hold him to account or get him to address the question is to interrupt him.

At one point he asked me if I had interrupted the last guy as much and someone in the audience shouted 'Yes'. Under questioning he promised to put the union ahead of Brexit and uphold the Barnett funding formula. He also said he didn't mind being called an a*se by his party colleagues who formulated 'Operation A*se' to stop him becoming PM last time round.

He didn't seem to keen on the question, but it was nothing compared to what was to come from the members. Flora asked if you had to be a "loyal husband and father" to be a good Prime Minister - he refused to answer and eventually said that he would have to live with people making up their own minds on that.

There were heckles from the audience and calls to move on, which I didn't. I hadn't raised the issue of character, they had. Lochie Spearman, whose father and grandfather had been Tory MPs, went on to call him a fibber.

None of this seemed to have much impact on the audience, the electorate in this contest. They liked Hunt, they loved Johnson. They seemed blown away by his celebrity, they enjoyed the entertainment, and, crucially, they think he can win. Not just the leadership election, that seems to be a foregone conclusion, they think he can win a General Election. They think he can beat Jeremy Corbyn and Nigel Farage and that's what they are voting for.

Tomorrow's debate still matters. It will be the first chance to see their next Prime Minister under the TV spotlight facing questions on his plans; but it probably matters more to non-Conservative party members than to those with a say in this election.