Hi, thank you for your question. Did the marriage actually take place in a Roman Catholic Church and do you have a marriage certificate?
Thank you for your question.
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Your husband is wrong and if he remarries without a divorce then he will be committing bigamy.
In fact UK nationals do NOT have to provide a Marriage Capacity Certificate, and even if they did and this had been overlooked this would NOT necessarily invalidate the marriage.
Please ask if you need further details