PIP assessment interview

I am my 16 year old son's representative for the PIP process. We have filled in the form and are awaiting an appointment for his face to face assessment.

My question is this: when we go for the interview what are my legal rights when they ask him questions - can they prevent me answering for him? I know that if the interviewer asks him "Could you cook a meal?" (for example) he will answer 'yes' when the true answer is 'no'. I am worried that he will talk himself out of any help he could receive, bearing in mind he has been on DLA for 9 years. 

I've read on forums how the interviewers can be really harsh and basically tell parents to shut up if they try to speak for their teenage child. I'm just wondering what my legal rights are.

  • I went through a pip assesement 2 years ago awarded high care and low mobility, she was really nice although she nothing of autism.  My g/f was asked a few questions, it was no where as bad as i thought.  I am been reassesed again now after 2 years, really does not help your anxiety levels.

  • It was quite a few years ago when my brother had his DLA medical at the age of 16 but it may be relevent. He was allowed to have the medical at home because of his autism. The doctor spoke with my mother and then my brother was called downstairs. He barely spoke and just stared at the ceiling so was allowed to leave without contributing. He was awarded middle rate care and lower rate mobility.