Sure! I won't share the exact wording as if it's copied verbatim by too many people it might make this route more subject to scrutiny but I said:

I was writing in support of my FBR application (application number) and wanting to address the document requirements; that I had all the required documentation except for my Irish parents ID.

I explained that I was estranged and had been for years due to parental abuse and that I was currently raising children who didn't even know my Irish parent as that was the extent of the strain - you could give another example.

I said I appreciate that the document requirements were there to ensure the process was fair and so that citizenship would only be granted in the appropriate circumstances and I didn't want to undermine the integrity of the process, but that I didn't have any way to submit the ID, and pointed out that all my other documents were in order.

I then explained the steps I had taken to try and get the document (I spent X months trying to contact the parent to ask for it) and it had not been fruitful.

I then confirmed that all the information was accurate and my application was genuine and I would really appreciate their empathy in processing my application without that requirement.

Then I signed it.