Having someone with me during a phone/video assess

When I attend PIP or ESA work capability assessments my husband always comes with me. I had assumed I had a right to have him present during a phone or video assessment but your advice says that I must ask permission first. I have never had to do that before. Do I contact the DWP before the assessment? What if they say 'no?' In the past I have never recorded or filmed an assessment. I know I would have to ask to do that first and I've never seen the necessity to do so as long as someone could be with me. I once attended an assessment without him and the assessor wrote things I was supposed to have said which I had not said.