Spain has arrested the police chief in charge of its economic crimes unit after €20 million was found stashed in the walls of his house, as part of an investigation into the nation’s biggest-ever cocaine bust, according to local media. Authorities reportedly arrested Óscar Sánchez Gil last week, along with 15 other people, including his romantic partner who is also a police officer in Madrid. Gil was until recently the head of the fraud and anti-money laundering division of Spain’s national police force. Police found €20 million hidden in the walls and ceilings of Sánchez Gil and his partner’s…