Safa and Marwa were born joined at the skull, they've never been able to see each other's faces.<br /><br />There are no official figures for how often this happens, but one estimate says craniopagus conjoined twins are born once in every 2.5 million births.<br /><br />Most do not live longer than a day.<br /><br />To separate them required multiple surgeries, months of hard work and the expertise of hundreds of hospital workers.<br /><br />The BBC was given exclusive access to Great Ormond Street as surgeons worked to separate the two girls.<br /><br />Video by Fergus Walsh, Rachael Buchanan and Laura Foster.
