Gwilherm Berthou

In 1929 he suggested to fellow chemist and Breton nationalist Célestin Lainé that a militant group dedicated to direct action against the French state and its symbols should be formed.

[citation needed] As Lainé sought his own recruits, Berthou brought the staff of the nationalist journal Breiz da Zont to join en masse.

When Lainé discovered this he distanced himself from Berthou, believing that a public journal could not create an effective support for a secret organization, as it would be too easily infiltrated.

"[1] However, when Gwenn ha du launched their first attack in 1932, bombing a sculpture, four informants claimed that Berthou had provided the nitroglycerin.

Along with Morvan Marchal and others he participated in the Kredenn Geltiek (Celtic Creed) Druidic group, adopting the bardic name Kerverziou, though also using the pseudonym "Iaktimagos Vissurix".