In July 1766 he was appointed secretary to the extraordinary embassy of William Nassau de Zuylestein, 4th Earl of Rochford to the court of France, and he wrote reports on the mission in 1766–1767.
[2] Letters to and from Porten went to the Marquis of Abergavenny's manuscripts, and occur in the official papers of Lord Grantham, Sir Robert Gunning, and others, now in the British Library.
William Coxe, in his Memoirs of the Kings of Spain of the House of Bourbon, 1700–1788, acknowledged his indebtedness to Porten's papers.
She was mother of Edward Gibbon, the historian, who spent in his grandfather's house at Putney in 1747–1748, cared for by his eldest aunt, Catherine Porten.
After her father's business ruin, she established a boarding-house for Westminster School, in which Gibbon lived, and which proved very successful.