The Serious Fraud Office (SFO) is set to reveal this week whether Barclays is to face criminal charges over a 2008 emergency fundraising from Qatar.
After a five-year investigation, the SFO is expected to announce its decision on Tuesday morning.
The probe has focused on whether commercial agreements between the bank and Qatari investors at the time of the fundraising were against UK law.
Qatar Holding invested in Barclays between June and October 2008, at the height of the financial crisis, when it was seeking extra cash.
The authorities have been investigating payments from the bank to Qatar around the same period.
The SFO has said it is “conducting a criminal investigation into certain commercial arrangements between Barclays Bank and Qatar Holding in 2008”.
The SFO and Barclays declined to comment.