What are they?
A pre-nuptial agreement (also known as a pre-marital agreement) is a written contract between a bride and groom-to-be that sets out to agree on how their assets are distributed (or remain theirs) should their marriage fail.

For many, the idea of entering into a marriage with a contract that deals with what happens in the event of the marriage failing seems to question their commitment to eachother. However, they are useful for marriages between couples where one has substantial wealth and the other does not.

Are they legal in the UK?
In the United Kingdom, pre-nuptial agreements currently have no legal standing. The divorce courts have the last word in the division of all matrimonial property and would ignore any pre-nuptial agreement if they thought that it was in any way unreasonable to either of the parties involved, particularly regarding to the maintenance and housing of children. For example, regardless of whose name a couple’s property is in, a court may order it to be transferred to the other. This applies to all property that is owned seperately or jointly

However, the rules for unmarried couples are quite different and legally binding contracts are enforceable so long as the couple remain unmarried. It is divorce that gives the courts jurisdiction to intervene and make orders. The widespread belief that long standing unmarried couples have rights as common law husband and wife is a myth.