FLR M, sponsor passport

[Rheinallt]

Hello.

My American wife and I are getting things ready to apply for her second 2.5 year spouse visa (FLR M). I don't have a British passport. I am a dual British/Irish citizen and the only passport I have is an expired Irish passport. Could anyone tell me if it is necessary for me to obtain a British passport in order to apply for my wife's flrm visa? If not, are there any other documents we can provide in place of it? Thank you.

[CR001]

What did you submit as evidence of your British citizenship with the initial spouse visa application??