English law on presumed undue influence is strange. This is the doctrine whereby if you're in a particular sort of relationship with someone with power or influence over you (say, a solicitor and client, parent and child, or priest and parishioner) and make a particularly noteworthy transaction with them (a contract, or a gift, say), they have to show you've had the opportunity to make your own mind up. (Or the courts can undo the contract, gift, whatever.)

If you're not in one of the special categories, the same thing applies but first you need to show that there's a relationship of "trust and confidence" between you. Fine.

What gets weird is that husband and wife is not one of the special categories. For a wife to claim her husband unduly influenced her she has to show there's a relationship of "trust and confidence" with her husband with respect to financial matters.

What's weirder is that being fiancés is. The law protects the fiancé as automatically vulnerable, and then as soon as the marriage vows are said the relationship's protection becomes conditional.