Complex sentence: On 1 May 1943 at Kensington Register Office, they married, and although her parents refused to attend, her governess "Portie" did, and they were allowed to live on the uppermost floor of her parents' house in Hampstead.
Split into simpler sentences: On 1 May 1943 at Kensington Register Office, they married, and although her parents refused to attend, her governess "Portie" did. The couple were allowed to live on the top floor of her parents' house in Hampstead.