He attended King's Mead School in Seaford, Sussex, then Eton and the Royal Military College, Sandhurst.
Geoffrey Keyes was commissioned into the Royal Scots Greys. He saw action at Narvik and was later attached to No. 11 (Scottish) Commando, which was sent to the Middle East as part of Layforce.
Following the allied invasion of Syria on 8 June 1941, No. 11 Commando was sent to successfully lead the crossing of the Litani River in Lebanon, fighting against troops of the French Vichy régime, during which Keyes played a leading part. In this operation, Keyes earned the Military Cross. Following the action, 11 Commando returned to Cyprus, then to Egypt in August 1941, where the unit was disbanded. Keyes was authorized to retain 110 volunteers as a troop in the Middle East Commando.
In October / November 1941 a plan was formulated at 8th Army headquarters to attack various targets behind enemy lines, including headquarters, base installations and communications facilities. One of the objectives was the assassination by a Commando team of Erwin Rommel, the commander of the Axis forces in North Africa. The raid was intended to disrupt enemy organization before the start of Operation Crusader.
The operation, codenamed Operation Flipper, was led by Lt. Col. Robert Laycock. Keyes, who had been present throughout the planning stage, selected the most hazardous task for himself: the assault on the supposed headquarters of Rommel's Afrika Korps established in a house near Beda Littoria. Following a landing by submarine and an exhausting approach march in torrential rain, Keyes tried to gain entry to the house but was confronted by a sentry. His fellow Commando Captain Robin Campbell fired several rounds at the sentry, one of which probably hit Keyes and led to his death a few minutes later. Most of the Commando team was eventually taken prisoner. Keyes was buried with full military honors in a local Catholic cemetery on Rommel's orders. It was later ascertained that the house was not Rommel's HQ, and indeed that he had been in Italy at the time of the attack.
Keyes was a member of the Marylebone Cricket Club.