An extract from the case referred to by STIDW:
"...the judge's finding, in respect of the health and wellbeing of the children, had gone beyond the sort of harm that children inevitably suffered when a marriage broke down and he had found that they had suffered significant harm.
He had further found, and been entitled to find, that both parties' conduct had contributed to the situation and that their presence together in the house was a problem. The judge had concluded that it was not possible for the parents to live together under the same roof without damage to the children. The parents themselves had seemed to be of the same view. In the light of those findings, it was not surprising that the judge had determined that he had to intervene. He had been correct, in determining how to intervene, to consider who should have care of the children.
Where one parent had had to be chosen as the primary carer, in the particular circumstances, the judge could not be criticised for having chosen the wife as it was not outside the band of reasonable decisions."
The crucial thing in that case was that the children were found to have been suffering "significant harm" (the test for taking a child in to local authority care). The harm has to go beyond the usual harm/upset suffered by a child in a family breakdown situation.
(Also don't think there was a typo - the court is saying that there's nothing in the statute that says that there must be physical violence otherwise the court cannot make an order - although absent physical violence it's hard to persuade a judge that's the right thing to do).