I've found a Charles Gardner working for Westley Richards as managing director. Gardner and Leslie B. Taylor held a patent in 1911 for a lever cocked hammerless gun with a pushed forward lever which doubles for the trigger guard. I can't find a Thomas Gardner however.
I found that reference in I.M. Crudgington and D.J. Baker's "The Bristish Shotgun" Vol. 3. Great books with tons of information. smile