It has been revealed that ETA's political chief, Francisco Javier López Peña 'Thierry', who was arrested in May 2008, was not only in charge of the gang's propaganda, but also made sure the "revolutionary tax" was paid, being directly responsible for extorting money from local businesses.

Although it has been shown that ETA stopped sending blackmailing letters in April 2011 (after the "permanent ceasefire" declared in January of the same year), extorting local buinesses had been, for decades, the main source of income for the terrorist organisation, accounting for around 80% of its income.

'Thierry' (pictured) admits that he had two 'postmen' - Juan Ignacio Otaño and Iñaki Iguerategui Lizarribar - working for him to deliver the letters to the businesses targeted by ETA. One of his computers held 1,863 files contatining blackmail details and it is known that over 1,800 letters of extortion were sent over one two-year-period, with 'Thierry' meeting secretly with his 'postmen' to hand over an envelope full of addressed envelopes and instructions on which month to deliver them.

Officers from the Guardia Civil followed and filmed Otaño delivering these letters in San Sebastián, as well as filming one of his meetings with 'Thierry' in France three days before he was arrested.

According to an analysis by the French justice system, who spoke to representatives of 125 Basque businesses, only 10% of victims ever alerted the police to their blackmail situation. Fear was the obvious motivation, with ETA having murdered 38 businessmen for not complying with their requests. ETA kept records of all 'requests' made and the planned repercussions in the case of non-payment. Sums as high as 32.5 million euros were extorted.