A woman who recently admitted giving her terminally ill seven-year-old son a large dose of morphine to end his “horrendous suffering” 40 years ago has died. Antonya Cooper, 77, made the admission in order to highlight efforts to change the law to allow assisted dying for terminally ill people. She said her own diagnosis of breast, pancreatic and liver cancer had reinforced her views on assisted dying. “We don’t do it to our pets. Why should we do it to humans?” she told BBC Radio Oxford last week. Her daughter, Tabitha, said Cooper was “peaceful, pain free, at home and surrounded by her loving family” when she died at the weekend. “It was exactly the way she wanted it. She lived life on her terms and she died on her terms,” she said in a statement to the BBC. The family had been visited by officers from Thames Valley police after Cooper’s interview about her son’s death, she added. Helping someone to die is illegal in the UK, but the prime minister, Keir Starmer, has promised to give parliamentary time to debate the issue. In 2015, MPs rejected moves to allow assisted dying by 330 votes to 118. But support for change has grown significantly among MPs and the general public. Opinion polls have shown 75% of the public back legalisation of assisted dying. Cooper, from Abingdon, Oxfordshire, said last week that her son Hamish had experienced “horrendous suffering and intense pain” as a result of his stage 4 cancer and “beastly” treatment. “On Hamish’s last night, when he said he was in a lot of pain, I said: ‘Would you like me to remove the pain?’ and he said: ‘Yes please, mama.’ “And through his Hickman catheter, I gave him a large dose of morphine that did quietly end his life.” Hamish had been diagnosed at five years old with neuroblastoma, a rare cancer that mostly affects children. He was initially given a prognosis of three months. After 16 months of cancer treatment at Great Ormond Street hospital, his life was extended but he was left in great pain, his mother said. She said: “I feel very strongly that at the point of Hamish telling me he was in pain, and asking me if I could remove his pain, he knew, he knew somewhere what was going to happen …. It was the right thing to do. My son was facing the most horrendous suffering and intense pain, I was not going to allow him to go through that.” She said she understood that she was potentially admitting to manslaughter or murder. After Cooper’s interview, Thames Valley police said the force was “aware of reports relating to an apparent case of assisted dying of a seven-year-old boy in 1981”. It added: “At this early stage, the force is making inquiries into these reports and is not in a position to comment further while these investigations continue.”