Soon after his marriage to the Jane Moses, Beauclerk, was approached by William Fitzwilliam, 4th Earl Fitzwilliam, to become a candidate for the Kingston upon Hull constituency in order to revive "the old Rockingham-Savile interest which before 1784 had been able to name one Member." Beauclerk felt unable to come forward without the support of Sir Henry Etherington, his wife's uncle and former guardian, who was sympathetic to sitting Member Walter Spencer Stanhope, who helped negotiate Aubrey's marriage to his heiress wife. After unsuccessfully approaching Francis Ferrand Foljambe, Fitzwilliam brought Beauclerk forward shortly before the 1790 general election and Etherington was persuaded to give his support. With the backing of Fitzwilliam, Beauclerk was able to force Stanhope's retirement and Beauclerk was elected. He represented the constituency of Kingston upon Hull from 1790 to 1796, but never spoke. "He sided with opposition in the Oczakov divisions," by pair on 12 April 1791 and by vote on 1 March 1792, and was a supporter of repeal of the Test Act in Scotland in 1791, but was listed a "Portland Whig in December 1792 and ceased to act with opposition." After the death of his father on 9 February 1802, Aubrey became the 6th Duke of St Albans, the 6th Earl of Burford, the 6th Baron Heddington, and the 3rd Baron Vere of Hanworth.
Personal life
On 9 July 1788, he married his first wife, Jane Moses. Jane was daughter of John Moses, of Hull in York, and his first wife Margaret Etherington, who died at or shortly after her birth. She had been raised by her stepmother, Margaret Cave Together, Aubrey and Jane were the parents of one child:
After his first wife's death on 18 August 1800, he married for the second time to Lady Louisa Grace Manners on 15 August 1802 in London. Lady Louisa was the fifth daughter of John Manners, MP, and Louisa Tollemache, 7th Countess of Dysart. The new duchess was said to have been "one of the brightest stars in the fashionable hemisphere" in the early years of her marriage. Together, they had one child:
Lord St Albans died on 12 August 1815, four months after the birth of his heir, the 7th Duke. His widow and son both died on 19 February 1816 and the titles were inherited by the 6th Duke's younger brother William, who became the 8th Duke of St Albans, who had thirteen children.
