https://www.gov.uk/government/publications/apply-to-make-decisions-on-someones-behalf-appoint-or-discharge-a-trustee-form-cop1d
Form COP1D: Apply to make decisions on someone's behalf (appoint or discharge a trustee) - GOV.UK
Use Form COP1D to give supporting information for your application to appoint or discharge a trustee as part of a Court of Protection order.