In 1872 he obtained a commission as an ensign in the 10th Tower Hamlets Rifle Volunteer Corps, rising to the rank of honorary colonel in 1888, and receiving the Volunteer Decoration in 1892. From the 1880s he was a member of the Shoreditch Vestry and in November 1885 was elected by the vestry to be a member of the Metropolitan Board of Works.
Wenborn remained a member of Shoreditch Vestry until it was abolished in 1900. The vestries and district boards that had been formed in 1855 were replaced by Metropolitan boroughs, and he was elected as a Unionist member of Islington Borough Council, holding his seat until 1912, by which time he was a member of the Municipal Reform Party.
He died in 1918 and was buried at Abney Park Cemetery.