PIP Mandatory Re-consideration

I wanted to share my experience with DWP today. I received a negative decision on my PIP application and so, following the advice here I wrote requesting a mandatory reconsideration. As I had not heard back and it had been 14 weeks since my letter, I called DWP today and was absolutely astonished as the response.

The individual confirmed that my letter had been received on 20th December 2017, but as I had not telephoned to say that I wanted a re-consideration, my letter was not registered on the system for it to be considered. The lady accepted that my letter was clear that it was requesting a re-consideration given that I had written MANDATORY RECONSIDERATION REQUEST as the subject of my letter but it was still ignored. I was told that she will register it and I will hear the outcome of the review within six weeks from today.

Has anyone else had this experience or is my case a one off?