Prince Frederick of Prussia (1911–1966)

He was the owner of Schloss Reinhartshausen [de] at Erbach, Germany. While staying there in 1966, he went missing and was found two weeks later after he had drowned in the Rhine. Whether it was suicide or an accident could not be determined.

He renounced his German citizenship in 1947. He was naturalised as a British citizen in October 1947 under the name Friedrich von Preussen (having also been known during residence in the UK as "George Mansfield"). This naturalisation was controversial, in part because being a descendant of Sophia of Hanover, and having rights under the Act of Settlement 1701, as amended by the Sophia Naturalisation Act 1705, he had a claim to British citizenship from birth. His status in context of his claim for compensation for property seized in Poland was debated in Parliament and the law courts until 1961.

Frederick married Brigid Guinness on 30 July 1945 at Little Hadham. They had five children:

He was studying at Cambridge and lived incognito as the Count von Lingen when war broke out in September 1939. He was arrested and interned in May 1940. He was held in Britain for several months and sent to internment camps near Quebec City and soon afterwards in Farnham, Quebec. In both camps, he was elected camp leader by fellow inmates.

Prince Frederick George William Christopher of Prussia (German: Friedrich Georg Wilhelm Christoph Prinz von Preußen; 19 December 1911 – 20 April 1966), also known as Friedrich von Preussen in the United Kingdom, was the fourth son of Crown Prince Wilhelm of Germany and Duchess Cecilie of Mecklenburg-Schwerin.