But if this man were the father of your kids and you were the woman who had ended up with broken bones, slashes and burns, you would not have the right to shut that door - not unless a judge had granted you an injunction to keep him away from your children. Most of the time this does not happen, according to an agonising Dispatches television programme to be broadcast this evening.
Viewers will be shocked to learn that our judicial system does not take domestic violence into account when deciding whether or not a child should carry on seeing a non-custodial parent after separation. With 160,000 divorces a year, thousands of children are affected by this failure of the law. The partner can be protected from further abuse, but vulnerable children, at least until they grow up to be teenagers, are forced to see these men even if it causes them untold terror.
Eight-year-old Timothy (not his real name) cannot understand why. He never wants to see his "first daddy", because he is horrible and because he remembers him hitting his mother. Yet Timothy's father, who had been kept for years in a psychiatric hospital, won the right to see him. It took several further court cases for Timothy to get the protection he needed.
Two young sisters, also featured in the documentary, describe how their father bangs their heads down on the desk or stabs them with forks if they make a mistake with their multiplication tables, and how they dream of him dying.
Yet the court ruled that the girls "benefited" from seeing their father. Some mothers have been imprisoned for refusing to follow such rulings. Sarah, a fragile woman with her pain bone-dry, recalls how she pleaded with court officials but failed to stop her husband getting access to Jack (three) and Nina (four), who frolic on a home video as she tells this story. The children were eventually killed by her husband, who then committed suicide. "It is too late," she says, her voice so gentle that you hardly hear her.
All this, you understand, is done in the "best interests of the child". Our society believes that a child will thrive only if both parents are present in his or her life. In an ideal world, and if the parents are conscientious, it is not a bad principle.
But it is insane and dangerous to make this into a pivotal, quasi-religious belief. In any case, it hardly stands up to any kind of rational scrutiny. If two biological parents are so essential, are children brought up by widows eternally damned? Would we allow a cruel adoptive father to have a child, because any father is better than none?
Taking this line negates morality and personal responsibility for actions. What are we teaching future generations about abusive behaviour within families if we tell children in such families that their love and loyalty for their brutalised mothers and their own suffering in the hands of a violent father are of no consequence? That, in effect, a single sperm cell gives a man immunity from social condemnation and inviolable rights over his product? We know from studies conducted in the United States since the Forties that juvenile offenders often have violent and alcoholic fathers. Angela Phillips, in her book, The Trouble With Boys, also points out that a man who beats up his partner "is going to teach his son that this is normal behaviour".
What is even more extraordinary is that we now have in place the Children Act, which was supposed to give vulnerable children a half-decent chance to make a go of their lives. It turns out that, in this area, the Act is more or less ineffective.
The first-ever research about children in contact with violent fathers after separation shows that many of these children are neglected and beaten and some are sexually abused during visits. In a quarter of the cases, the fathers were drunk and one in seven of the children was left on its own.
What makes it worse - and the children say this - is that the mothers are not there to safeguard them. Dr Lorraine Radford, an expert on children and domestic violence, is convinced that we need a radical rethink of the law in order to stop the legally sanctioned victimisation of already traumatised children.
Why have we allowed this situation to develop? I think the reasons lie deep within our social attitudes to children. We still think of them as our possessions, commodities and chattels, to be divided up neatly after divorce. The Dickensian father may have become the stuff of costume drama, but the Victorian assumptions of paternal power still determine our laws and behaviour. In our wisdom we rely on the truism: "He is, after all, the father."
This means that whatever he does, however bad he is, some distant moment of ejaculation gives a father rights that should never, ever, be taken away. As one articulate 10-year-old points out in the programme: "Anyone can father a child. But that doesn't mean they can be a dad."
We need urgently to change the law, although the Lord Chancellor's Department appears to have no plans for this in the near future. According to some senior family lawyers, it may even be possible to use the existing Children Act to change practice by introducing new guidelines for judges and court welfare officers who make the assessments on whether or not children should see their fathers. These officers are not trained in child psychology nor the effects of domestic violence. Jack and Nina died because the officer in charge did not understand the psychotic condition of their father.
But, most of all, we need to talk to the children and to treat them as equal citizens in our society. They are individuals who must be entitled to participate in decisions about parental contact. This will not happen unless we understand that we have no absolute rights over our children, but that as caring adults we must promote and protect their rights. We may give them life, but their lives are not our property. And in the end, you have to earn the privilege of parenting by proving that you are worth it.
`Dispatches' will be shown on Channel 4 this evening at 9.30pmReuse content