Bertie was born Thomas Hoar on 3 July 1758 in Stockton-on-Tees, County Durham, the sixth child and fourth son of George Hoar, the Keeper of the Regalia of England at the Tower of London, and his wife Francis. His name was entered into the books of the yacht HMY "William &amp; Mary" in March 1771, when he was just twelve years old, but this was only for seniority, and he spent his early life being educated, first at a navigation school in his native Stockton, followed by a move to London to attend Mr Eaton's academy, and then Christ's Hospital. He first went to sea in October 1773, joining the 24-gun under Captain George Farmer. Also serving aboard the "Seahorse" as midshipman and able seaman respectively were the young Horatio Nelson and Thomas Troubridge. The three future admirals became good friends and would remain in correspondence with each other throughout their lives. Hoar transferred to the 50-gun under Commodore Sir Edward Hughes on 27 June 1777 at the instigation of Hoar's patron, Lord Mulgrave, and returned to England on 14 May 1778. He was promoted to lieutenant on 21 May that year, and appointed to serve aboard the 74-gun under Joshua Rowley. With Rowley he was present at the Battle of Ushant on 27 July 1778, and in December moved with Rowley to the 74-gun .