Mikel Lejarza Eguía was a member of the Spanish intelligence service

Centro Superior de Información de la Defensa

Centro Superior de Información de la Defensa was the Spanish intelligence agency before the current Centro Nacional de Inteligencia took over as its successor in 2002.-History:...

. During the 1970s, he worked undercover

Undercover

Being undercover is disguising one's own identity or using an assumed identity for the purposes of gaining the trust of an individual or organization to learn secret information or to gain the trust of targeted individuals in order to gain information or evidence...

 as a double agent

Double agent

A double agent, commonly abbreviated referral of double secret agent, is a counterintelligence term used to designate an employee of a secret service or organization, whose primary aim is to spy on the target organization, but who in fact is a member of that same target organization oneself. They...

 infiltrating the Basque separatist organisation ETA. The secret service knew him by the nickname El Lobo (The Wolf). Lejarza provided safe houses for ETA in Spain to lodge ETA's commandos.

As a result of Lejarza's long-time operation, a major police operation against ETA took place in 1975, resulting in more than 150 arrests and a number of alleged summary executions by the Guardia Civil. They were considered political prisoners and were released when Juan Carlos I became king some months later.

A movie about his life, El Lobo

El lobo

El lobo is a 2004 film directed by Miguel Courtois. It stars Eduardo Noriega.-Plot:Lobo is based on the life of Mikel Lejarza, an agent of the Spanish intelligence service in the 1970s...

, was made in 2004. His appearance has been surgically altered and he is still a target for ETA assassins.