Her brother George was reinstated as king in 1935, and Katherine returned to Greece with her sister, Irene. She joined the Greek Red Cross when the Second World War broke out in 1939. In 1941, after Greece had been overrun by Axis forces, she fled to South Africa with her third brother, Paul, in a Sunderland flying boat, where she worked as a nurse at a hospital in Cape Town. She heard no news of her sister Helen for four years. She returned to England in 1946, sailing the last leg from Egypt to England on the Cunard liner RMS "Ascania". On board, she met Major Richard Campbell Brandram MC (5 August 1911 – 5 April 1994), an officer in the British Royal Artillery. They were engaged three weeks after they arrived in England, but their engagement was announced only in February 1947. On 1 April at the Royal Palace, three weeks prior to the wedding, her brother King George had a stroke and died shortly after in Katherine's presence. George was succeeded on the Greek throne by Katherine's third brother Paul, who acted as best man at the wedding, which took place according to schedule on 21 April 1947.