Peter Ivan Lake was born in Surrey in 1915, but grew up in Majorca, where his father was British consul. He read Modern Languages at St John's College, Oxford, and was working for a merchant bank in Ghana at the outbreak of war. He managed to make his way back to England, and was eventually commissioned into the Intelligence Corps, where he served with the Field Security Police before being recommended to SOE by a chance acquaintance.

After a brief period of training, his first assignment sent him back to West Africa, and the Spanish-ruled island of Fernando Pó in the Gulf of Guinea. In January 1942 the Italian liner Duchessa d'Aosta sailed into Santa Isabel accompanied by two smaller vessels. Lake, working at the British consulate, enticed the crews to come ashore, while a small SOE force aboard the Maid Honor, a converted trawler, quietly took command of them and towed them out to sea. Aside from SOE's material gains, the success of 'Operation Postmaster' proved Lake's ability to hold his nerve and maintain his cover - the Spanish authorities took no action against him after the incident.

He laid low until his return to England in August 1943. Being too well known in Africa, he was transferred to F Section, which trained him for the role of liaison officer and instructor. After doing well on courses at Beaulieu and Howbury Hall in Bedfordshire, he was picked to join Jacques Poirier's newly formed DIGGER, which had just been given the job of taking over from Harry Peulevé's AUTHOR circuit in the Corrèze and Dordogne, Peulevé and three of its members having just been captured. He parachuted with wireless operator Ralph Beauclerk on the night of 9/10 April 1944, landing safely near Domme on the southern bank of the Dordogne, where they were greeted by Poirier and one of his local reception committees.

Despite his less than perfect French, Lake was largely left to his own devices, as Poirier had planned to spend several days in Paris. Introduced to a young maquis leader named Soleil, he was quickly acquainted with his group and told that if he did not agree to arm them, Lake would be shot. Although impressed by the extraordinary zeal of Soleil, he soon managed to distance himself from him, and began working with other less volatile maquis leaders across the Dordogne, including 'Carlos', who commanded groups of Spaniards around Périgueux. Lodged with Poirier, Poirier's Alsatian dog, Dick, Beauclerk and several others at a deserted chateau near Limeuil, Lake and his companions became an effective and close-knit team; when they were joined by writer André Malraux, he chose to christen them the farfelus (madcaps).

On the night of 4 June Beauclerk received the coded BBC message 'the giraffe has a long neck', which signalled that D-Day was imminent. DIGGER began disrupting trains and other communications: Lake enthusiastically took to obstructing the northwards advance of the Panzer division Das Reich, which was held up for several days, and blew up 500 yards of track at Neuvic to permanently block rail access to Périgueux. Following a massive Allied airdrop in July, Resistance forces were able to bring about the surrender of the German garrison at Brive-la-Gaillarde on 15 August, and Lake appeared in a British uniform specially flown in for the occasion.

With German forces rapidly retreating from south west France, Poirier sent Lake to begin an operation to attack an enemy detachment on the island of Oléron, off the Charente-Maritime coast. Within days of arriving he heard rumours that de Gaulle was visiting the nearby town of Saintes, and decided to accompany several French officers to greet him. However, Lake was crestfallen when the General simply declared 'we don't need you here', and demanded that he return to England immediately: unknown to him, de Gaulle had already issued the same directive on his tour, demanding the removal of F Section organisers Roger Landes and George Starr. Despite this snub, France did at least recognise Lake's work, later making him a Chevalier of the Légion d'honneur and awarding him the Croix de Guerre; he also received the Military Cross.

Lake's post-war life was spent working for the Foreign Office, and included postings to Iceland, Syria, Indonesia, Paris and Venice. More than a decade after meeting de Gaulle, he was re-introduced at a reception in Brazil, during which their previous disagreement was finally laid to rest. Retiring in the mid-1970s, Peter Lake returned to Cambridge, where he died in June 2009.