 Lady Rosebery 's eldest son , Harry , who was less successful in politics than his father and brother , distinguished himself by becoming captain of Surrey County Cricket Club and owning two Epsom Derby @-@ winning horses . He succeeded his father as 6th Earl of Rosebery and died in 1974 . Margaret married her father 's old friend and biographer the Marquess of Crewe . Such was still the fame of her parents that London traffic was brought to a standstill on her wedding day in 1899 . Lady Crewe became one of the first women magistrates in Britain ; she died in 1955 . Lady Sybil has been summarised by one of her father 's biographers : " Even more eccentric than her father , she spent much of her time living in a caravan . " Neil , the second of the Roseberys ' sons , entered politics and a promising future was <unk> for him . However , on the outbreak of World War I he joined the army , and was killed leading a charge at <unk> in 1917 . 
