Before I write this I am going be on the side of caution and take my daughter's passport but....

travelling down to London with my daughter for the weekend (internal flight) and can't find if I need ID for her. Given we won't check bags and BA never ask for ID - although other airlines do - I should be OK and I fear I will lose her PP without my wife!! But it will be sods law - just wondered what the official line is anyone know?