Thank you for replying.
I have read many works on canon law and annulment. They all say the same thing. Every marriage is putative until the contrary is shown.
Just because someone knew a Catholic got married in the local register office does not mean her/his marriage is not valid. To say it is not is simply gossip rather than fact. If John Smith married Mary Green in Blackburn Register Office on 11 August 2018 and John Smith is a Catholic it is gossip to say John Smith and Mary Green are not validly married because John Smith is bound by canonical form.
The Bishop of Salford, or someone lawfully delegated by him, may have granted John Smith dispensation from canonical form. Therefore, his marriage in the register office was not invalid.
That is why any marriage is putative until all the facts are properly ascertained by those appointed by the Church to do that. Admittedly, not every case requires the formal process before a tribunal. Some may be quickly dealt with by an administrative procedure. However, all cases require proper evidence.
The marriage mentioned above is a fictitious example and to the best of my knowledge relates to no real persons, living or dead. The English town of Blackburn is in the diocese of Salford.