If the ex wont agree.
I am getting married tomorrow and dd1 will be the only one with my maiden name double barrelled with his. She wants to take my married surname but i know know know he will not let her. Can she just let herself be known by this name as long as she uses her real name for important documents and then when she reaches the right age change it herself by deedpoll? She is 8 by the way and cannot stand him and hasnt seen him for over 2 years yet he still keeps dragging me to court