A cautionary tale can be found here

In contemplation of marriage (or civil partnership) is an old-fashioned phrase but actually has a good deal of relevance in modern Will-writing as more people are living in long-term relationships prior, if ever, to getting married.

In simple terms, if an unmarried couples make Wills and there is any chance that they may enter into marriage at some stage in the future, it makes very good sense to make the Wills - In contemplation of marriage.

The reason for this is that the act of marriage (civil partnership) will automatically revoke any Will previously made unless the Will has been made - in contemplation of marriage. Thus following a marriage each party can automatically become intestate and the rules of intestacy may not in many circumstances meet their requirements.

This may be particularly important in a second marriage situation where one or both parties wish to protect each other whilst still maintaining the interests of their children from their first marriage. Often such a couple may make a Will before marriage incorporating an appropriate trust type but if they later marry without making the Wills - in contemplation of marriage - their best laid plans will be lost and they will need to go to the expense of making another Will after marriage or remain intestate.

The phrase - in contemplation of marriage - is a such a very important tool in Will writers armoury and should always be considered where appropriate.

Of course, if a relationship breaks down after making a Will - in contemplation of marriage, it is equally important that a new Will is made to reflect the new circumstances of the individuals in question.

(As an aside, I once acted for a couple who planned to get married and I made Wills- in contemplation of marriage, for them. No more that 3 months later the man returned with another lady and made a further Will in contemplation of marriage, The disappointed potential bride followed shortly afterwards to amend her Will. At least everyone had been trained well in their legal duties regarding their Wills!)