A lesbian has been given custody of her former partner’s children after a landmark court ruling decided she could be considered their “natural parent.”

The woman, who cannot be named for the children’s protection, had been granted shared contact of her ex girlfriend’s seven and four year old daughters, until the mother broke the order by moving away.

This action breached a court order and prompted the High Court to grant primary care to the former partner, which was confirmed at the Court of Appeal earlier today.

The head of the panel, Lord Justice Thorpe, said: “We have moved into a world where norms that seemed safe 20 or more years ago no longer run.”

He asked, “Who is the natural parent?” In the past judges have ruled that the biological parent is the natural parent, “but in the eyes of the child, the natural parent may be a non-biological parent who, by virtue of long-settled care, has become the child’s psychological parent,” he said.

He decided that since the couple had both raised the children, there was no distinction of a biological relationship.

The biological mother, who also cannot be named, was referred to as CG, she gave birth to the children, A and B, after insemination by an anonymous sperm donor during her relationship with ex partner, CW.

The couple broke up in 2002 after seven years together but was still granted access to the children by the Court of Appeal after a previous restriction.

The panel at the time, also headed by Lord Justice Thorpe, ruled that same-sex partners should have the same rights as estranged heterosexual couples and therefore CW was awarded joint residency rights which would be “vital” for the children’s psychological health.

The mother was refused consent by CW’s solicitors to take the children to Cornwall but she still sold her Leicester house and registered her offspring at a Cornwall school without telling CG.

Lord Justice Thorpe said: “This, of course, was a flagrant breach of the court’s control of the arrangements for the children and an elaborate deception of CW.”

The court heard that CW realised the children were missing and contacted the mother’s solicitors who said she had acted against the court in the interests of her children.

The mother had been given primary care by the High Court Family Division in February but CG took the case to the Court of Appeal where today’s decision was made.

Lord Justice Thorpe said: “As in the present case, the family may be created by mutual agreement and with much careful planning. Both partners seek the experience of child-bearing and child-rearing in one capacity or another.

“There, as here, the care of the newborn, and then the developing baby, is broadly shared, the children will not distinguish between one woman and the other on the grounds of biological relationship.”

Panel member, Mrs Justice Bracewell’s said she had “no confidence that if the children stay in Cornwall that CG would promote the essential close relationship” with her former partner’s family.”

Lady Justice Hallet, another panel member dismissed the appeal “with a degree of hesitation”.

She said: “I am very concerned at the prospect of removing these children from the primary care of their only identifiable biological parent who has been their primary carer for most of the young lives and in whose care they appear to be happy and thriving.”