Sponsor letter and certification of passports

[aussie21]

I just have a question in relation to applying for a spouse visa my husband has three passports German, British Australian does I have to include all three on my application and does he have to get all three certified by the appropraite consulate ie germna, british etc

Also the sponsor letter does it have to be signed it's just that normally I would write something like this up and he would just sign it because he is flat off his feet working and taking care of our child in the UK.

[CR001]

British passport as that is the only one relevant to a spouse visa application.

Sponsor letter not mandatory, the form contains all the information HO are interested in.