Sir Hector Sants is taking time off work at scandal-hit Barclays because of stress and exhaustion.
Sants, who was appointed chief executive of the UK financial sector regulator at the start of the crisis, is head of compliance at Barclays and charged with ensuring the bank's staff adhere to laws and regulations.
A statement from Barclays said of Sants that "rather than carry on working, and risk more serious consequences to his health, he is following medical advice and will be taking a leave of absence until the end of the year."
Sants worked at the Financial Services Authority (FSA) from July 2007 to July 2012. He has also worked with the Bank of England on regulating the financial sector.
Before turning gamekeeper, 57-year-old Sants worked at investment bank Credit Suisse as its EMEA chief executive.
He is not the first senior banker to have taken time off for stress. In 2011, Lloyds Banking Group Chief Executive António Horta Osório went on sick leave for the same reason, but forewent his bonus for the year because of it.
Hants started compliance work at Barclays amid a torrent of investigations and accusations fired at the bank by global regulators.
Barclays has been mired in a series of financial scandals, including Libor fixing, PPI, and derivatives mis-selling.
As a result of probes by US and UK regulators, Barclays was slapped with a combined £290m fine for its traders' attempts to manipulate Libor, a keenly watched benchmark rate, in order to benefit their trading positions.
In the first half of 2013, Barclays set aside another £650m to compensate customers who were mis-sold complex interest rate hedging products, bringing the total compensation pot up to £1.5bn.
Barclays also revealed that it was hit by a £1.35bn PPI charge.
While the bank said it has made a total provision of £5.45bn, almost £3bn has still not been paid out to victims of the mis-sale of PPI and interest rate swap agreements (IRSA).