Complex sentence: In the mid- 1930s, Hutch is rumoured to have had a lengthy affair with Edwina Mountbatten which scandalized the British upper classes, becoming the subject of tabloid fodder, and an embarrassment to Lady Mountbatten's royal in-laws.
Split into simpler sentences: In the mid- 1930s, Hutch is rumoured to have had a lengthy affair with Edwina Mountbatten. The rumour scandalized the British upper classes, becoming the subject of tabloid fodder, and an embarrassment to Lady Mountbatten's royal in-laws.