A form of marriage registration has been required from earliest times, unlike births & deaths.
Before 1849 a marrige could only be legally performed in the Established Church and hence was recorded in the Parish Register.

After March 1884 all marriages, civil or religious, had to be notified to the civil authorities.

Thus there is a feint possibility of a legal marriage between 1849 and 1884 not being in the civil registry and not being in a PR.