A High Court judge has sanctioned the sterilisation of a man "in his best interests" in a landmark legal ruling.The 36-year-old, from the Midlands, has learning difficulties and already has a son, born in 2010, with his girlfriend.Mrs Justice Eleanor King ruled that a vasectomy could take place after hearing that another child could cause the man "psychological harm".Experts said he was capable of sexual consent but did not have the capacity to make decisions about contraception.They said the man, referred to as DE, could not be relied upon to use condoms or other birth control methods effectively to prevent pregnancy.The Court of Protection in London has heard that DE does not want to become a father again.'Relationship strain' The case came to court because of undisputed evidence that DE does not have the capacity to decide whether or not to consent to sterilisation, meaning a judge had to make the decision.In her ruling, Justice King said DE lived with his parents but had a long-standing, loving relationship with his girlfriend PQ, who also has learning disabilities.The birth of the couple's first child had a "profound" effect on both families, and measures were taken to ensure there was no further pregnancy, including supervision of DE at all times.The judge said the couple's relationship "nearly broke under the strain, but remarkably weathered the storm".She said it was now "lawful and in DE's best interests" that he should undergo a vasectomy and all "reasonable and proportionate steps" should be taken to enable the operation to go ahead.The application to allow a vasectomy was made by the man's local NHS trust, with the support of his parents, GP and the local authority involved in his care. None of them must be identified, by court order.An application for the sterilisation of a man came to court in 1999 but was refused, making the new ruling the first time in England and Wales a court has sanctioned a man's sterilisation.