Refused uk Visa due to incorrect information sent in error

[art11]

Hi
I am hoping someone here could advise me on this matter, we applied for a settlement visa a couple of months ago and were refused quite rightly due to our mistake as we put down that we had both been married or in a civil relationship in question 1.20 and 1.21 of VAF4A- Appendix 2 which was wrong as neither of us have been married or civil partnership prior to our marriage this year, what we put down was our previous relationships which we had in the past. (Silly mistake really)
The question is? as we are going to reapply as soon as possible, What evidence should we supply to prove we were single before our marriage on the 14th June 2017, would a sworn affidavit by both of us be sufficient????

Thanks for reading

Art11