Chaps ... I could not help being intrigued to read the "debate" between the two of you. Here, then, are MY conclusions - based on the copy we kept from a year past March when Myrna applied for naturalisation - using the National Checking Service operated by Edinburgh City Council:-

Whilst TWO referees are required to complete and sign Section 5 of Form AN, only ONE of them need act as a countersignatory on the reverse side of the passport~size photo.

So, no harm done, Mark ... Jane successfully obtained her British Citizenship. And that, after all, is what matters most!

Congratulations to BOTH of you.