Re-Marrying

Dear Learned Team,
Have a question on behalf of a friend. He is a UK citizen but during UK passport application he did not mention his previous marriage and subsequent divorce as he thought it was not relevant because the marriage/divorce did not take place in UK. Under the circumstances, if he wishes to marry now in UK or overseas by declaring his previous divorce in the marriage registration process, will it cause any issue in future as his marital status was declared single in the UK passport application despite being divorced overseas ?

Thanks