 After commissioning , the ship spent several months conducting sea trials and training until August , when she began the necessary modifications to serve as a royal yacht for the forthcoming royal tour of South Africa . The Admiral 's suite was reworked into accommodations for the Royal Family and their staff while the anti @-@ aircraft mount on top of ' B ' turret was replaced by a saluting platform . Agnew was promoted to rear @-@ admiral with effect from 8 January 1947 . The alterations were complete by December , and Vanguard made a shakedown cruise into the Central Atlantic and made a port visit to Gibraltar on the return voyage . Initially escorted by the destroyers Orwell , Obedient , Offa , <unk> , and Rotherham , the ship rendezvoused with the Home Fleet on 1 February 1947 to receive a 21 @-@ gun salute led by the battleships Nelson and Duke of York , and the aircraft carrier Implacable . Later that morning , a Sikorsky R @-@ 4 helicopter landed aboard to pick up mail and photographic film . 
