[3][2] Horner was a member of the executive and finance committees and of the council of the National Union of Conservative and Unionist Associations, and at the 1895 general election was an unsuccessful candidate for the constituency of Southwark West.
[5] In 1902 and 1903 Henry Labouchère, Liberal MP for Northampton alleged that Horner had obtained cash or credit from a number of hotels on the Continent using company cheques which were not honoured by the bank.
[7] By the time of the general election called in January 1906, he had been disowned by the Conservative Party, who nominated another candidate for his Lambeth North seat.
[5] In July 1906 Horner failed to attend a bankruptcy hearing, his medical witness stating that he was "confined to his bed, suffering from complete mental prostration".
He claimed to have witnessed the Liberal leader, David Lloyd George, being assailed by an angry group of voters in Falmouth, Cornwall.