From 1886 to 1890, he served as Lieutenant in the 3rd Battalion Northamptonshire Regiment and in 1890, he was Second Lieutenant with the Royal Horse Guards. Lord Rosslyn succeeded his father in the earldom on 6 September 1890, inheriting the family seat, Rosslyn Castle in Midlothian, Scotland and Rosslyn Chapel, collieries at Dysart, a luxury steam yacht, and assets of £50,000. His mother, the dowager Countess of Rosslyn, survived his father by over 40 years before her death at Regent's Park, London, in December 1933. From 1890 to 1897, he was Captain of the Fifeshire Light Horse Volunteers, serving with Alexander Thorneycroft's Mounted Infantry during the Second Boer War where he was taken prisoner twice, which he wrote about in his book Twice Captured. After his bankruptcy, he resigned his commission in the Fife. Lord Rosslyn was war correspondent for the Daily Mail in 1900. In 1904, he was Secretary to the Secretary of State for Scotland and from 1915 to 1917, he was Major in the King's Royal Rifle Corps.
Gambling problem
Lord Rosslyn was a notorious gambler, betting £15,000 on Buccaneer to win the Manchester Cup, which lost. He played the roulette tables at Cannes and Monte Carlo, which he wrote about in his autobiography My Gamble With Life. By 1896, he had lost everything and was declared bankrupt, which led to the family silver, gold and silver plate being sold at a three-day auction in Edinburgh. In 1902, he lost £310 while playing poker. In 1903, he was in Court for refusing to pay a $150 draft. In 1908, Rosslyn and Sir Hiram Maxim were in the news for a gambling duel in Monte Carlo to "break the bank".
Personal life
On 19 July 1890, Lord Rosslyn was married to Violet Aline Vyner, the second daughter and co-heiress of Robert Charles de Grey Vyner of Gautby Hall and Newby Hall by his wife Eleanor Shafto. At their wedding the Prince of Wales, later Edward VII, proposed the health of bride and groom. Lord Rosslyn was a close friend of the Prince who became godfather to his son. Before their divorce in 1902, they were the parents of:
Lady Rosabelle Millicent St Clair-Erskine, who married Lt. David Cecil Bingham, second son of Maj.-Gen. Hon. Sir Cecil Edward Bingham in 1912. After he was killed in action in 1914, she married Lt.-Col. John Charles Brand, eldest son and heir of Maj. Hon. Charles Brand, in 1916.
After their divorce, Lady Rosslyn married the English race car driverCharles Jarrott in 1903. On 21 March 1905, he was married to an American actress, Anna Robinson, the second daughter of George Robinson of Minneapolis, Minnesota. They divorced in 1907 and Anna later died on 4 October 1917. His third marriage took place on 8 October 1908 to Vera Mary Bayley, a daughter of Eric Edward Bayley of Little Moyle in County Carlow. Together, they were the parents of:
Lady Mary Sybil St Clair-Erskine, who married Sir Philip Dunn, 2nd Baronet, a son of Sir James Dunn, 1st Baronet, in 1933. They divorced in 1944 and she married, secondly, Capt. Robin Francis Campbell, only son of Rt. Hon. Sir Ronald Hugh Campbell in 1946. They divorced in 1958 and she married Charles Raymond McCabe in 1962. They divorced in 1969 she remarried her first husband, Sir Philip.
Maj. Hon. David Simon St Clair-Erskine, who married Antonia Mary Kelly, the only daughter of Admiral of the FleetSir John Donald Kelly in 1948. They divorced in 1958.
Lord Rosslyn died on 10 August 1939 and was succeeded by his grandson, Anthony. His widow, the dowager Countess of Rosslyn, died on 24 February 1975.
