Ernest Augustus was himself an heir to the British titles of Prince of Great Britain and Ireland, recognised "ad personam" for Ernst August's father as well as for him and his siblings by King George V of the United Kingdom on 17 June 1914, Duke of Cumberland and Teviotdale, Earl of Armagh, which however were all suspended under the Titles Deprivation Act 1917. In addition to being a German, he also held British nationality, after successfully claiming it under the Sophia Naturalization Act 1705 in the case of "Attorney-General v. Prince Ernest Augustus of Hanover". Nonetheless, a problem arose as foreign royal titles can't be entered into a British passport. Therefore, the titles "Prince of Hanover, Duke of Brunswick and Lüneburg" could not be mentioned there, nor could the British titles due to the Titles Deprivation Act of 1917. The name which was finally entered into his British documents, was thus "Ernest Augustus Guelph", with the addition of "His Royal Highness". "Guelph" is thus also the British last name of his siblings and children, all styled "Royal Highnesses" in the United Kingdom.