Benjamin Bloomfield Trench was born 12 November 1846 to Henry Trench of Cangort Park, Shinrone, County Offaly and Georgiana Mary Amelia Bloomfield, sister of the 2nd Lord Bloomfield of Loughton House. He was educated at Eton. He worked as a mechanical engineer for Maudsley & Fields and later with William Steuert Trench in his land agency office at Carrickmacross between 1868 and 1870. He was also employed by Verner & Holleborne stockbrokers to manage quarries in Antrim. In 1872 he was employed by Lord Bath to take over the management of the Bath estate following the death of William Steuert Trench, but was relieved of this position in 1874. He married Dora Turner in 1899 and moved to South Africa to work on the Transvaal Railway. He returned prior to the birth of his two daughters Sheelah and Theodora Trench.
William Steuert Trench employed Benjamin Bloomfield Trench in his land agency office in Carrickmacross, County Monaghan from 1868-1870. When the former died in 1872, Lord Bath employed B. B. Trench as his land agent until 1874.