The children in question were born in 2021 through a donor-assisted human reproduction (DAHR) procedure in Ukraine, with the use of the man’s sperm and donated eggs.

The woman who gave birth to the children — who is their mother, despite having no genetic link to them — claimed that the man had agreed to donate sperm but was never meant to have an ongoing role in the lives of the children.

The man alleged that there was in fact an unwritten co-parenting agreement from which the woman resiled.

In a judgment handed down last year but published this month, Ms Justice Nuala Jackson found that “prior to and at the initial stages of the pregnancy, it was envisaged by all concerned that the applicant would have an ongoing, hands on, role in relation to the child/children if conception was achieved”.

The position of the respondent “fundamentally altered over time”, she said.

The judge held that the man had “proved parentage of the children on the balance of probabilities”, despite the woman’s failure to comply with a previous court order to facilitate DNA testing, which she criticised.

“It is important to note that this declaration of parentage is a scientific matter, unrelated to the welfare of the children,” the judge said.

While expressing some “concerns”, Ms Justice Jackson appointed the man as a guardian of the children on an interim basis.

“Overall, I believe that this is in their best interests but, in so deciding, I would hope that the applicant would use this position not to cause disruption to the children’s lives or to advance opposition towards the respondent,” she said.

“She is and always will be the children’s mother and her role as such should be promoted and supported by the applicant.”