He was commissioned as Lieutenant in the British Army on the general list[3] On 1 August 1940 a motorboat attempted to land three French agents: Clech, Tilly, and Victor Bernard at Carentec in Brittany but had to abort the mission after coming under fire and returned to England.

[4] In Operation Delay II Peter Churchill’s mission was to land four SOE agents on the French Riviera by submarine.

[7][6] They travelled in the submarine HMS Unbroken to Antibes where on the night of 21 April 1942 Churchill took Newman and Zeff and their radios to the shore by canoe, and led them to their contact Dr Élie Lévy.

[8] Clech became the radio operator of Inventor network of Sidney Jones ("Élie"), with Vera Leigh ("Simone") as courier.

[4] On the night of 14 May 1943 he was brought by Lysander piloted by Hugh Verity with Sidney Jones and Vera Leigh to set up the Inventor network.