Harriett Cowper was baptised in Hertingfordbury, Herefordshire on 12 July 1733.

She was a cousin of the poet William Cowper who had an unhappy romance with her sister Theodora.

William had a long correspondence with Harriet, even though there was a 19-year gap where at Harriett's insistence they did not communicate.

Harriett eventually broke the silence with a letter of congratulation to Cowper when his second book of poetry was published.

[2] After Cowper's death in 1800, Hesketh corresponded for the rest of her life with his cousin Dr John Johnson, with whom he had spent his final years.