On 4 September 2017, Diamond sailed for a 9-month deployment to the Middle East, initially scheduled to relieve HMS "Monmouth", she was instead diverted to take over as flagship of Standing NATO Maritime Group 2 from sister HMS "Duncan" when her intended relief, HMS "Ocean" was redeployed to provide relief to British Overseas Territories in the Caribbean in the wake of Hurricane Irma. "Diamond" was relieved of her NATO duties upon the return of "Ocean" from the Caribbean on 30 October and resumed her planned deployment to relieve "Monmouth." However, on 23 November, The Times reported that "Diamond" was being forced to abandon her deployment and return to Portsmouth early due to mechanical issues, which was later confirmed by the Ministry of Defence.