[1] After training as an architect,[2] Lonsdale established a long partnership with the architect William Burges, working with him as his principal artist on many of Burges's major commissions,[1] including Saint Fin Barre's Cathedral,[3] Cardiff Castle,[4] Castell Coch and the Yorkshire churches.

"[1] He also designed the zodiac windows and celestial ceiling at Mount Stuart House[6] and the silver casket in which the heart of Burges's great patron, John Crichton-Stuart, 3rd Marquess of Bute was transported to Jerusalem for burial in 1900.

Without the master's control, much of his later work tends to be mechanical and vapid.”[8] An exhibition of Lonsdale's work, organised by the Yale Center for British Art, was held at Gallery Lingard in 1984.

[9] A collection of Lonsdale illustrations and cartoons, for the decoration of Mount Stuart House on the Isle of Bute where it is held, was catalogued in 2022.

[10] In the same year, an exhibition held at the house, Fantasy to Fabrication: 19th century design at Mount Stuart, included examples of Lonsdale's art.