You asked

How many prisoner to prisoner civil partnerships have there been yearly going back as far as possible and the same for prisoner to prisoner same sex marriage.

It would also be helpful to know how many of these were prisoner to prisoner civil partnership/marriage between prisoners both detained in the same prison.

We said

Thank you for your request.

Marriage and civil partnership statistics are based on information recorded on the marriage and civil partnership registration; however we do not hold any information which enables us to identify prisoners who marry or form a civil partnership.

We have also contacted the General Register Office who are responsible for recording marriage and civil partnerships and they do not hold this information either. We are therefore unsure where this information can be obtained.