In fact, this is what it says in the official guidance:
Under section 7.1 a gift from a third party can be the source of cash savings held by the applicant, their partner or the couple jointly, provided that the money has been held by them for at least the 6 months prior to the date of application and is under their control.
And:
7.4.1. Savings must be held in cash in a personal bank/savings account in the name of the applicant, their partner or the couple jointly. The savings can be from any legal source, including a gift from a family member or other third party, provided the source of the cash savings is declared. The applicant and/or their partner must confirm that the money, which cannot be borrowed, is under their control and evidence that it has been held in their bank account for at least the 6 months prior to the date of application.
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