Katherine was born and raised in Barnsley, South Yorkshire, England. As the daughter of Irish parents, Katherine spent much of her childhood in County Kerry, Ireland and was also schooled in America, where she lived for a number of years. At age eighteen she was awarded a place at the prestigious Royal Academy of Dramatic Art (RADA) in London, where she was classically trained for three years. Since graduating in 2001, Katherine has worked continuously in Theatre (Royal Shakespeare Company, The National, Donmar Warehouse), Television (Criminal: UK, Cheat, Happy Valley, Mr. Selfridge, Coronation Street), Film (Dirty God, Official Secrets) and Radio (BBC 3 and 4).