'Abortion, transgender rights, same sex marriage, if you don’t accept them then you’re a right wing scumbag...I’m used to that...'

“Abortion is the taking of human life,” Robertson says. “There is no way round that. It is a baby in the womb. I think if people were aware of that they would be less supportive of it. We can show all kinds of horrors on television. Yet you can’t show an abortion. Why can’t people see what an abortion actually is?”

It's not as if the public is unaware of what an abortion is - and in fact, although abortions have rarely been televised, Channel 4 broadcast a documentary which contained images of aborted foetuses at ten, 11 and 21 weeks. Last year a New Jersey abortion counsellor controversially shared a film about her own abortion on Youtube, though it showed no detail of the actual procedure, just her face throughout the experience.

Robertson believes that, as it stands, there is “not enough education about abortion.”

“There isn’t enough information. People don’t know what an abortion actually is. And I think immediately if people became more aware of what abortion is you would lessen abortion. People say they are pro-choice, but if you’re going to make a choice then you need all the information you can get if you make that choice. And I believe that if people knew how the baby developed in the womb then there would be much less chance of abortion.”

The devolution of abortion law to Holyrood is already fuelling a tense debate. Pro-lifers view it as a chance to bring the maximum time down, and to prompt wider debate, particularly around the notion that some babies can survive outside the womb, with medical support, at the same age as others can be terminated. The pro-lifers want to take on the status quo, seeing devolution as a chance to chip away at abortion rights already here. What's more, the tabling of abortion law into the Scotland Bill was itself, in part driven by them.

The Don’t Stop A Beating Heart campaign draws attention to the fact that a foetal heart starts beating at 18 days. It plays on a slogan that has long had a currency in the pro-life movement in America, appearing on billboards and bumper stickers: “Abortion stops a beating heart”. But it will also serve as a reminder, for many, of the tragic death of Savita Halappanavar who was refused a termination at a hospital in Northern Ireland - where the 1967 Abortion Act does not extend - on the grounds that her foetus, while unviable, still had a beating heart.

For Robertson the point of the campaign is “partly to prevent further liberalisation but also that we would also like to see the number of abortions reduced and we would like to see the age limit cut.” What he favours is a cutting to the time limit of 12 weeks, which he calls the “European norm”, since it is shared by France, Germany and Italy. He worries, he says, that with the devolution of abortion law “there will be groups who will argue for a loosening of the restrictions, particularly from two doctors to one”.

It’s a fear that is either exaggerated or misplaced, since, in fact there seems to be little or no political appetite or campaigning for extending the time limit. Ann Henderson of Abortion Rights Committee Scotland has said “this is not a debate about time limits”, but about “supporting legal, safe access to abortion as provided for under the 1967 Abortion Act”. Nicola Sturgeon has declared: “A vast majority of abortions take place well before 20 weeks, there's a tiny proportion between 20 and 24 weeks. I don't believe there is evidence that backs up a reduction in the time limit and, more importantly, I've never seen any evidence that reducing the time limit for abortion reduces abortions. What it does do, or what it risks doing, is sending abortions back to the back streets and making them less safe for women."

Robertson feels the issue has become so “politicised that any form of sensible discussion is not allowed.” And while both sides seem keen to avoid it escalating to the vitriolic intensity it has reached in the United States, a tension is building. “Just look at the atmosphere in America,” says Robertson. “I don’t want that. I think those that are for abortion are trying to create that. For example they say that people like me and this campaign have right wing American funding. We say it’s not American funding at all, and it’s not right wing.”

Abortion, Robertson believes, is partly such a key issue because of the role it has to play in Scotland self-defining itself as a progressive country. “There is a kind of myth being built up that there are certain signs that we are progressive. One of those signs that you are progressive because you are for abortion.”

Robertson almost always uses the word baby rather than foetus. “Nobody speaks about the royal foetus, they always speak about the royal baby,” he says. “If someone in my congregation miscarries or loses a baby, I’m not going to them saying, don’t worry, it’s just a collection of cells. They know that’s rubbish.”

He gives an example, an old story from when he was a young minister, of a 16-year-old girl at one of his youth clubs, who came to him, burst into tears and told him she'd had an abortion. When he asked her why she was upset, she replied, “The bastards lied to me. They said it was like having a wart removed. But it was a baby wasn’t it?” Robertson recalls replying, “Yes I think it was. And I think there’s forgiveness and help for you. But yeah you’re right. I’m not going to lie to you and say, it’s just a collection of cells.”

He describes images and footage he has seen of abortions which he says he would not be allowed to campaign with. “People promote the idea of choice and information, but then they say, ‘Oh no that’s not fair, because it’s scaremongering’. But it’s reality.” Among the procedures he describes to me is one called “partial birth abortion”, a procedure now illegal in America, and which has barely ever been practised here. “In partial birth abortion the baby was partly taken out of the womb and its head was crushed. It’s absolutely horrendous. It’s astonishing.”

Of course, both sides of this often vitriolic debate complain about each other’s tactics. “There was a rather disgusting campaign,” Robertson recalls, “in the United States where women were being asked to wear t-shirts, proudly boasting that they had had an abortion.”

Often he mentions the use of abortion “as a contraceptive”, saying: “I think there were 11,475 abortions in 2014 and 3675 were repeat. If you’ve got a third doing repeats, this is no accident. I am opposed to using abortion as a type of contraceptive. I fear that would happen if abortion law was liberalised.”

Again, there is the consistent concern that the law is to be liberalised, although there are no plans for liberalisation - which seems to undermine the entire raison d'etre of the new campaign.

So, when does he think an abortion is the right thing? What about a woman carrying a severely disabled child? He has described our current approach as "a war on the disabled in the womb".

“The case for abortion,” he says now, “is always put in terms of extremes. People say, 'What about the severely handicapped?’ But the vast majority of abortions in Scotland [are carried out on the grounds] that greater harm would be caused to the mother by continuing with the pregnancy than having the baby. I think that there were less than 150 that were for handicap.”

What about women who have been the victims of rape? “If there was a baby that was six weeks old,” he says, “and that baby was a product of rape, would we have the right to kill him or her because they were the product of rape. The answer is no.” He adds: “I’ve met people who have said to me I’m so glad my mother didn’t abort me even though my father raped her.”

And what about very young mothers? Dundee where he has his ministry has for many years topped the tables for teen pregnancy and also for abortion rates, at one time even coming out as teen pregnancy capital of Europe. “You want to reduce teenage pregnancies,” he says, “don’t go around telling girls if you get pregnant you can just have an abortion. Of course no one’s directly saying that to them, but the subliminal message is there.”

Yet, Robertson says that he is not an absolutist. He is not saying all forms of abortion would be wrong. “There may be extreme circumstances where abortion is the lesser evil. But what I’m saying is they are extreme circumstances. Never use extremes to make laws.” The circumstances he talks of include “where the baby is dead or has no chance of being born alive; where the life of the mother would be lost.” In those cases, he says, you are “choosing the lesser of two evils.”

Robertson believes abortion has become a “shibboleth” in our culture, along with transgender rights and same sex marriage. “If you don’t accept them then you’re a right wing scumbag. And I’m used to that, I get that all the time. My fear about what is happening is that there’s a liberal, metro elite, usually wealthy people, privileged people, who say this is how it should be.”

Indeed human rights themselves, in their current form, are something he views with scepticism. “I think that the new religion of our country is human rights, but human rights as defined by a specific group of people. We’ve got a kind of new priesthood in my view, who are defining human rights. I want to challenge that.”

"I believe in human rights," he adds, perkily. "For me the right to live is a basic one - and I think the child in the womb is a human."