The gang had located an empty property two streets away from a Banco Popular branch in the centre of Elche, a city in eastern Spain.
They began their ‘work’ a month before the planned robbery, telling inquisitive neighbours they had been employed to do up the empty house.
“Three or four of them would arrive at 10 every morning with their tools and then leave at lunchtime like most builders do,” one resident told Spanish daily El Mundo.
The men were in fact carefully digging a half a metre-wide tunnel, avoiding electricity lines, gas pipes and sewers in the process.
But when the “expert gang” reached the bank after closing hours, a security guard alerted police of a torchlight he had spotted in one of the security cameras.
Sources close to the investigation believe the robbers escaped in the nick of time through the tunnel, probably alerted by a lookout they had working for them outside the bank.
Police, who have combed the tunnel and sewers looking for clues, are convinced the robbers were intending to blow up the vault over the weekend when the streets of Elche’s city centre are deserted, especially during the summer months.
Their investigation is still underway.