A long-awaited fraud trial of four former Barclays executives will begin this week over charges related to a £12bn rescue package secured from investors including Qatar at the height of the financial crisis.

The court case brought by the Serious Fraud Office (SFO) will see the former chief executive John Varley, ex-investment banking chief Roger Jenkins, former Barclays Wealth boss Thomas Kalaris and ex-European financial institutions head Richard Boath face charges over conspiracy to commit fraud in relation to the 2008 capital raising. All four have pleaded not guilty.

It is part of the first criminal case in the UK to pursue senior bankers for events surrounding the financial crisis.

But the trial, which is expected to last at least 12 weeks and is scheduled to begin at Southwark crown court in London on Monday, will also put the SFO’s reputation on the line, after two of its high-profile cases were scrapped this year alone.

Charges against former Tesco executives, accused of being masterminds behind a major accounting scandal, were thrown out in December after a judge deemed the case too “weak” to face a jury. The SFO is believed to have spent about £10m pursuing the former managers.

The SFO also saw its case against Barclays bank – which is separate to the case against the ex-bosses – over the Qatar fundraising dismissed by the court in Southwark last year. The SFO later lost a high court appeal to reinstate those charges.

The court failures were embarrassing for the SFO, which also faced criticism for the collapse of a 2016 trial against brokers accused of helping the convicted trader Tom Hayes rig the Libor rate.

The SFO’s original charges against Barclays and the former executives followed a five-year investigation into the details of the rescue package secured over a decade ago.

The cases relate to a £12bn rescue package provided by investors including Qatar Holdings in 2008, which helped Barclays avoid a government bailout during the banking crash. The investigation centred on a subsequent $3bn (£2.3bn) loan to state-owned Qatar Holdings, which was allegedly used to buy Barclays shares in what the SFO says amounted to unlawful financial assistance.

The charges against the four former executives were first made public in 2017, with Varley losing two major board positions following the SFO’s announcement. The 62-year-old promptly stepped down from the board of asset manager BlackRock that summer, and was also replaced as the chairman of the Marie Curie cancer charity.

Varley was a Barclays stalwart, having joined in 1982. He also had close familial ties with the bank after marrying Carolyn Pease, whose Quaker family sold their own bank to Barclays in the early 1900s. He served as chief executive from 2004 to 2010.

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Jenkins, the former investment banking head who is also facing charges, was once believed to be Britain’s highest-paid banker, earning £40m per year, and was best known for setting up the bank’s controversial tax advisory business, which was later wound down. He left Barclays in 2009.

Kalaris left Barclays in 2013, but went on to co-found the wealth management firm Saranac Partners three years later. Boath, meanwhile, stayed on at Barclays until 2016 but claimed he was unfairly dismissed over an interview he gave the SFO during its investigation into the Qatar deal. The employment tribunal is on hold until the SFO case is settled.

Barclays still faces the threat of a £1.5bn civil case over the Qatar funding later this year. The case is being brought by the businesswoman Amanda Staveley through her firm PCP Capital Partners, alleging fraudulent misrepresentation and deceit over the terms given to potential investors of the emergency fundraising. Barclays said in its annual report that it planned to defend itself against the claim, with the trial expected to start in October.