We are taking DP's 15-yr-old out of the country for the May half-term. He's close to 6 ft and clearly couldn't be exported against his wishes 
DP is actually the resident parent, but I don't think that is apparent from the passports and I guess it may be seen as a bit unusual. They share surname.
Can we just rock up at passport control? Or do we need a statement of permission from his Mum? And if we do need her permission, will a generic letter do, or does it have to be verified by a solicitor etc?
It's all amicable. If we need a letter from Mum there isn't an issue with getting it. It's more a question of do we need to pay someone to verify her signature?