Harmonie-Rose Allen, an eight-year-old girl, has become the youngest person in the world to use prosthetic legs with computerised knees.Thanks to her new prosthetics, she says she can go on walks with friends and keep up with their pace.During an appearance on Good Morning Britain, Harmonie-Rose also showed how she can stand up and sit down without needing any help.Harmonie-Rose had all her limbs amputated after she contracted meningitis when she was just ten months old.GMB, ITV