The Financial Conduct Authority (FCA) has reopened an investigation into events surrounding the discovery of "misconduct" in Halifax Bank of Scotland's (HBOS) Reading-based impaired assets team.
The regulator will seek to determine what people within HBOS knew of the bad practices at the firm and its communications with the Financial Services Authority - the FCA's predecessor - after the initial discovery of the misconduct.
HBOS was embroiled in a complex multi-million pound corruption and fraud case involving bank employees and private business advisers dating back more than a decade.
HBOS parent Lloyds Banking Group (LBG) estimates the compensation for investors caught up in the incident will total £100m.
The regulator had put its investigation on hold at the request of Thames Valley Police in early 2013, while the force undertook its own probe into the events.
Six people were jailed for a total of 47 years and nine months following Thames Valley Police's investigation. Five people, four men and a woman, were found guilty on 30 January of corruption, fraudulent trading and money-laundering offences. One man was acquitted and another man had pleaded guilty at an earlier hearing.
Senior investigating officer Detective Superintendent Nick John described the six-year investigation as "the longest and most complex case in Thames Valley Police's history".
LBG chief executive Antonio Horta-Osorio said: "As I have stated before, we would like to express our deep regret and apologies to any customers directly affected by the criminal behaviour of these individuals. We are absolutely determined that victims of the crimes committed at HBOS Reading are fairly, swiftly and appropriately compensated."
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