Marmont was born in 1912.

He obtained his wings on 26 April 1935 and was transferred to 802 Squadron on 4 February 1939.

On 1 July 1938 he was promoted to Flight Lieutenant.

When the war broke out Lieutenant Marmont served with 802 Squadron on HMS Glorious. At this time the unit was equipped with nine Sea Gladiators and formed part of the complement of the carrier under the command of Lieutenant Commander J. P. G. Bryant.

When war was declared HMS Glorious was sent to join HMS Eagle in the Indian Ocean for trade protection duties.

On the way HMS Glorious off loaded three aircraft at Kalafrana, Malta, the other six remained under the command of Marmont.

On 1 March 1940 Marmont was promoted to operational commander of the 802 Squadron.

In April 1940 HMS Glorious was ordered home to take part in the Norwegian campaign. She was chosen because her “T” shaped lifts permitted larger aircraft such as the Gladiator and Hurricane to be struck below. HMS Glorious arrived at Scapa on the 18 April having re-embarked the three aircraft she left at Malta.

802 Squadron was reorganized on HMS Glorious’s arrival in the Clyde on 17 April, and they rejoined the ship on 22 April 1940 off Scapa Flow, with nine aircraft, together with 804 Squadron, also with nine aircraft, for operation off Norway.
HMS Glorious was also carrying seventeen Gladiators and one Sea Gladiator belonging to 263 Squadron, which was being transported to Norway,

Together with 802 Squadron Marmont took part in both the Norwegian campaigns.

On 1 May, during the evacuation of the first Norwegian campaign, HMS Glorious operated together with HMS Ark Royal off the Norwegian coast. During the early morning at about 07:00, two of 802 Squadron's Sea Gladiators intercepted a lone Do 17P of 1(F)./120, which had just discovered Vice-Admiral Well's force. The Dornier was left in a damaged condition but the alarm had been raised. A force of Ju 87Rs from I./StG 1 took off from their base in Norway, led by two He 115s of 2./KüFlGr. Arriving over the naval force, one group of Stukas bombed HMS Glorious but failed to achieve any hits. The other group were driven off by a section of Sea Gladiators.
At 15:00, Blue Section from 804 Squadron (Lieutenant Richard Smeeton, Acting Sub Lieutenant R. R. Lamb and Lieutenant Taylor) engaged a He 111 at 16,000ft. Two of the pilots were able to get in a short burst each before the Heinkel escaped. 20 minutes later another Heinkel was spotted but the Sea Gladiators could not get close enough to open fire.
At 16:30, Red Section from 804 Squadron (Lieutenant R. H. P. Carver, Lieutenant C. E. F. Gibson and Sub Lieutenant Michael Fell) took off to relieve Blue Section. Not long after take-off a lone raider was seen at low altitude. This was chased off and the section climbed up to 18,000ft. Not long after they were ordered to intercept another lone aircraft, again at low altitude. A He 115 was observed low over the water and despite a long chase, in which all their ammunition was expended, the Heinkel escaped.
At this point an enemy raid was detected on radar and further sea Gladiators were scrambled from HMS Glorious to intercept. Blue Section from 802 Squadron scrambled two Sea Gladiators at 18:00 and these were followed 15 minutes later by a section from 804 Squadron. The 802 Squadron pair, led by Lieutenant Marmont, went after another lone raider, possibly a He 115, but this escaped. By this time the 804 Squadron section had become engaged with a force of six Ju 87s. Lieutenant Marmont had also joined the fray and getting in behind one of the Stukas, Marmont shot it down into the sea west of Namsos at 18:25. The crew of Oberfeldwebel Erich Stahl and Unteroffizier Friedrich Gott from 2./StG 1 were rescued by a Royal Navy destroyer.
Lieutenant Commander John Cockburn of 804 Squadron took part in the attack on the remaining Ju 87s and reported:

"At 1825 hrs, six Ju 87 dive-bombers were sighted three miles ahead on an opposite course in open "V" formation. The order was given to open fire, and the section half-rolled individually onto the tails of the aircraft, each pilot attacking one enemy. Fire was maintained in short bursts, as the enemy twisted and turned, until the final bombing dive was commenced. The attack was broken off at this point, as I imagined, quite erroneously, that the pom-pom fire would take effect below this."

Marmont then took part in the second Norwegian campaign but was lost when HMS Glorious was sunk by the German battlecruisers Scharnhorst and Gneisenau on 8 June.

He was posthumously mentioned in despatches on 25 June 1940.

At the time of his death, Marmont had claimed one shared victory, this one being claimed while flying Gloster Sea Gladiator.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1940
	01/05/40	18:25	½	Ju 87 (a)	Shared destroyed	Sea Gladiator		W Namsos	802 Squadron

Biplane victories: 1 shared destroyed.
TOTAL: 1 shared destroyed.
(a) Ju 87R of 2./StG 1 crashed into the sea west of Namsos at 18:25. Oberfeldwebel Erich Stahl and Unteroffizier Friedrich Gott picked up by a British destroyer.

Sources:
Fledgling Eagles - Christopher Shores with John Foreman, Christian-Jaques Ehrengardt, Heinrich Weiss and Bjørn Olsen, 1991 Grub Street, London, ISBN 0-948817-42-9
Gloster Gladiator Home Page - Alexander Crawford.
Gloster Gladiator vol. 1 Development and Operational History - Alex Crawford, 2009 MMP, ISBN 978-83-89450-59-3
Royal Navy Aces of World War 2 - Andrew Thomas, 2007 Osprey Publishing, Oxford, ISBN 978-1-84603-178-6
The Commonwealth War Graves Commission
The London Gazette
Additional information kindly provided by Mark Horan.