Ownership and income tax: Specific types of property: bank and building society accounts - legal and beneficial ownership
Banks and building societies in the UK operate on the basis of the legal ownership and have no need to query the actual beneficial ownership.
The fact that an individual is named on an account does not necessarily mean that they are the beneficial owner. If they are named, it means they can draw on the account. But the ability to withdraw money does not imply any beneficial ownership. It is the entitlement to income as it arises that is important, not by whom capital or income is withdrawn.