Mary Lee Bennett married James Tregaskis in 1887. Her first husband, William Parsons Bennett had died the previous year, and Mary had inherited his bookselling business, which had traded in Birmingham and London.
James and Mary established a new shop ‘at the sign of the Caxton Head’, at 232 High Holborn, where it was described in glowing terms in William Robert’s 1895 guide for bibliophiles, The Book-Hunter in London: ‘The chief and most enterprising firm of booksellers in Holborn proper is that of Mr. and Mrs. Tregaskis, at No. 232, the corner of the New Turnstile… the two together have built up a business which is scarcely without a rival in London.’ They sold a wide range of books and manuscripts, advertised in as many as twenty catalogues a year. Many of the manuscripts were acquired at auctions, and a manuscript was typically relisted in Tregaskis catalogues every three months. Some manuscripts remained in stock for many years. The Tregaskis catalogues often featured covers with imaginative images of medieval figures admiring books, suggesting that the Tregaskises saw medieval manuscripts and rare books as an important part of their stock.
Following Mary’s death in 1900 James continued the business until his own death in 1926, moving the shop to Great Russell Street in 1915. The business was then continued by James’ second wife, Eveline, and children until 1939.