Born on 18 March 1854, he was the son of the distinguished Shakespearian scholar, Clement Mansfield Ingleby (1823–1886) and his wife, Sarah Oakes (d. 3 January 1906),[4] of whom he contributed an interesting memoir to the Dictionary of National Biography.
In 1919 and 1923 he edited the Red Register of King's Lynn, described in The Times as "a collection of records of no little importance for students of social life and organization in England during the 14th and 15th centuries."
At the December 1910 general election he stood as Conservative candidate for the borough, and defeated the former member, the energetic and independent Thomas Gibson Bowles by a majority of 97.
Three humble voters confessedly backed by more powerful people, lodged an election petition against the new member on the ground that he and his agents had been guilty of bribery and corruption.
At his house, Sedgeford Hall, a few miles away, he had habitually received vast parties of guests, providing them with "pageants and carnivals," not to speak of refreshments, the attendance numbering 7,000 in 1905 and 3,000 in 1909.