Born on 28 September 1871, eldest child and only son of Hugh Ainsworth and his wife Mary Wright Joynson, he was educated at Owen's College and the Royal Infirmary, Manchester, qualifying in 1895 with first-class honours and serving as house physician; he was also assistant medical officer at the Monsall fever hospital. Ainsworth was commissioned as a Surgeon-Lieutenant in the Indian Medical Service on 29 July 1896 and saw active service in the Tirah campaign on the North-West Frontier. For his part in the actions at Chagru Kotal, Dargai Sampagha and Arhanga passes, and in the operations near Dwatoi and in the Bara valley, he was awarded the medal with two clasps. Thereafter he pursued the ordinary routine of Indian service, was promoted Captain in 1899 and, after taking the Fellowship in December 1907, became a Major on 29 January 1908 and Lieutenant-Colonel in 1916. He was made Colonel in 1923, and appointed an honorary surgeon to the King on 27 August 1924. He retired on 28 September 1928. Ainsworth married in 1909 Laura Delaforce, who survived him with their two married daughters. He lived at 1 Ellardale Road, Bognor and died on 13 February 1952 at the Royal West Sussex Hospital, Chichester, aged 80.