Unlike Neligan, Lily Mernin never publicised her activities. She was a member of the Keating Branch (Dublin), Gaelic League, whose members included Collins and many leading IRA commanders. Referred to by Collins as 'Lt. G." (Little Gentleman), Mernin, according to IRA Director of Publicity, Piaras Beaslai, began spying in November or December 1919. Amongst other information she supplied the names of the British spies slaughtered by the Squad in Dublin on 21 November 1920. Written as" Lt G" in IRA literature to avoid her discovery if documents were captured.
Frank Thornton says Mernin was" a typist at Comand HQ of Dublin District, the Intelligence Branch of which was under the control of Col Hill Dillon, Chief Intelligence Officer" and that she put the IRA in touch with staff in different departments of the British in Dublin Castle. He believes that she should get a large amount of the credit for what the IRA learned from inelligence. She worked mainly with Frank Saurin . Dalton WS says Military Intelligence operated out of Dublin District office in Royal barracks. Lillie Mernin was their only contact there
W.S. no. 715 made by Colonel Frank Saurin, who was a member of G.H.Q. Intelligence, he mentions Lily Mermin, quote-
One of my chief agents was a Miss Lily Mermin, a cousin of Piaras Beaslai. She was a typist in Dublin Castle and did typing work for Collins at 118 Clonliffe Road, the home of Pat Moynihan. Moynihan was a postal official in the Sorting Office, Rotunda Rink, and was the agent who gave us the information which led to the various raids on enemy mails. In addition to Lily Mermin being one of our agents at Dublin Castle, she was also attached to me for visiting hotel lounges and the like for spotting and identification work of enemy personnel who used to frequent such places.She and my wife used to attend whist drives run by F. Company Auxiliaries in Dublin Castle. It was usual for one or two of the Auxiliaries to see the ladies to the tram.I followed from outside the Castle, all the time taking a mental description of the men- height, colour, features, clothes, etc. Subsequently I was given their names, rank and official position. un-quote.