Four. This is how many times the whistle-blower who uncovered a massive alleged money laundering scheme at Danske Bank’s Estonian branch said he had notified his superiors about suspicious transactions. But no action was ever taken.

“It’s fundamentally unclear to me… why the executive board didn’t take action,” Howard Wilkinson, the British former head of the lender’s market business in the Baltics, told a Danish parliamentary commission on November 19.

As reported by the Agence France-Presse (AFP), Wilkinson compared whistle-blowers to smoke detectors. He said at Danske Bank, “the smoke detector went off four times, there was a huge fire. The smoke was filling all the corridors. Not only did the bank ignore the smoke detector, but the bank actively tried to switch the smoke detector off.”

According to an outside law firm that carried out a probe for Denmark’s largest lender, more than 1.5 trillion Danish kroner transited through the Estonian subsidiary of Danske Bank between 2007 and 2015.

Danske Bank has said it is impossible to say how much of the gigantic sum was dirty money but has admitted that many of the suspicious transactions could be “criminal”.

AFP note that of the around 15,000 accounts under investigation – which Danske Bank closed in 2015 – 6,200 are considered suspicious and most of them have been brought to the attention of the authorities.

The bank has been unable to specify exactly where the money came from. It has said 23% of the incoming funds were from Russia.

Also speaking before parliament, the bank’s interim chief executive, Jesper Nielsen, acknowledged there had been a “lack of focus and understanding about the scope of the problem”.