He joined the army, receiving a commission in the Durham Light Infantry in 1940 and was subsequently recruited into the Special Operations Executive (SOE).
In November 1942 he was sent into France to join the newly formed Prosper network, but on June 23, 1943 was arrested by the Gestapo. together with cell leader Francis Suttill and courier Andrée Borrel.
Norman was taken to the Paris headquarters of the Sicherheitsdienst at 84 Avenue Foch and tortured for several days.
The Germans used Norman's captured wireless set, to transmit their own false messages to SOE Headquarters in Baker Street. Norman attempted to warn London that he was in captivity by not giving the German's the second part of his security check, which they did not know about, but was frustrated when London sent a curt reply telling him to correct the omission.
The Germans were thus able to set a trap which resulted in the capture of Jack Agazarian who had been sent with Nicholas Bodington to investigate the fate of the Prosper network.
After brutal interrogation and torture, Norman was shipped to Mauthausen concentration camp where he was executed on September 6, 1944.
Major Gilbert Norman is honored on the Brookwood Memorial in Surrey, England and as also on the "Roll of Honor" on the Valençay SOE Memorial in the town of Valençay, in the Indre departément of France.