After spending days / weeks filling in the form beforehand with plenty of backup information on good and bad days and how it affects you - this is completely ignored by the the assessor who claims to be an expert then asks purely yes/no questions & will not allow you to explain how things change on a daily or even hourly basis.
Re the Forms - The first lot that I filled in mysteriously 'disappeared' and I had to do them again. Fortunately, my partner had photocopied the originals so the second lot was easier (for her!). I make a point of keeping copies of all forms and letters that I send to the DWP or anyone else relating to the 'Benefit/Jobcentre' system. You'll have to forgive my cynicism, it has been acquired by years of bitter experience .