When you marry, your assets become 'matrimonial assets' and unless specifically protected, can be considered for division as part of divorce proceedings. The main purpose of a prenuptial agreement is to limit potential claims on the assets of one of the parties to the marriage, thereby avoiding costly litigation.
At present, prenuptial agreements are not legally binding in England and Wales, however, courts may take them into consideration, as long as certain safeguards are met.
In Scotland, prenuptial agreements are regarded as legally binding provided that they are fair and reasonable at the time they are entered into.