The eldest son of William George Mount of Wasing Place, Berkshire and wife Marianne Emily Clutterbuck, he was educated at Eton College and New College, Oxford where he achieved honours in classics and modern history.
He was called to the Bar by the Inner Temple in 1893. Between 1896 and 1903 he served as assistant private secretary to two Chancellors of Exchequer, Sir Michael Hicks Beach (later Viscount St. Aldwyn) and Charles Thomson Ritchie (later Baron Ritchie of Dundee).
After his father stepped down as member for the South, or Newbury division of Berkshire in 1900 he was elected and served for six years before being defeated at the 1906 general election by his Liberal opponent. In the January 1910 general election he stood again and succeeded in regaining his seat where he remained until resigning in 1922.