Deterioration of condition

Like many others I've been dreading PIP ever since it was first announced years ago. A few weeks ago the dreaded letter arrived telling me my DLA was ending and that I needed to claim for PIP - great timing on the part of the DWP - 2 months after my mum died, weeks away from a major operation, and just after a major restructuring at work was announced!

But I digress…I had an indefinite DLA award of low rate care (on the cooking a meal grounds) and high rate mobility (on distance I was able to walk grounds). Since the award was made in 2008 my condition's actually gradually deteriorated, but I haven't told the DWP (yes, I do know, not very bright!!!).

I figured that as I was already on high rate mobility, the distance I can walk deteriorating wouldn't make any difference, and there was no change to my ability to cook. As PIP had been announced I figured they'd be wanting me to claim PIP imminently anyway, and having read all the horror stories about PIP, didn't want to do anything that would hasten the dreaded transfer. I've basically spent the last 9 years being terrified of that brown envelope landing on the doormat.

My question is, should I: include a covering letter with the claim form explaining that I've gradually deteriorated and why I didn't tell them, should I somewhere on the claim form (probably under Q15) explain this, explain in Q14 on moving around about the deterioration in my condition, or just leave the form as it is (I've gone into a lot of detail for each question on exactly how my symptoms affect each activity)?

Thank you in advance for any guidance.

Thank you for clarifying that BIS. That was my initial intention, but then I had 'last minute' jitters when I came to completing the mobility section.