The investigation into the financial practices of Iain Coucher, the former boss of taxpayer-backed Network Rail, is expected to conclude in the next two to three weeks.
It is widely expected that Mr Coucher will be exonerated over serious financial impropriety, though he might be criticised over the human resources practices under his tenure.
Antony White, a leading QC and a colleague of Cherie Booth at Matrix Chambers, has spent months interviewing witnesses and asset tracing to prepare his report into the financial affairs of Mr Coucher.
An internal investigation by the big four accountant PricewaterhouseCoopers has already cleared Mr Coucher, who was chief executive from 2007 to 2010, of any wrongdoing. The allegations are of misuse of public money – for example, Mr Coucher and his business partner, Victoria Pender, receiving £180,000 for unspecified services to Network Rail.
He was also accused of living "a James Bond lifestyle", using his vehicle allowance to pay for the running of his Aston Martin.
A former colleague of Mr Coucher was quick to defend the criticisms of his expenses. "There's this suggestion of excess," he said. "It does not look good, but this is really a matter of tone and taste. Iain has also essentially been accused of fraud. This is serious, nasty stuff but I've been through all of the accounts and I'm very confident that he's innocent."
The HR issues include using public money to pay off aggrieved staff before they went to tribunal. There are also reported to be allegations of sexual harassment.
Network Rail, which is now headed by London 2012 Olympics builder David Higgins, could do with a positive report. Last week it was fined £3m over the Potters Bar derailment, finally drawing to a close the fallout from a crash that happened nine years ago.
Jarvis, the maintenance contractor at the time, has long been accused of being at fault for the disaster in Hertfordshire, which killed seven people. However, the now-defunct company was working to a safety regime established by Railtrack, Network Rail's predecessor body.
Jarvis was also initially charged in this court case, which was brought by the Office of Rail Regulation earlier this year. However, this charge was dropped in March as Jarvis is now in administration, so there was virtually no chance of any fine being paid out.
Former senior executives at Jarvis are known to be pleased that Network Rail has finally been sanctioned over the derailment. Many executives felt that the company had unfairly taken the brunt of the criticism over the years.
Network Rail is expected to trim parts of its maintenance budget to cover the fine. Mr Coucher did not put a provision in Network Rail's accounts to allow for any potential legal case and resulting fine.
In 2005, British Transport Police concluded that there was little chance of a successful prosecution ever being made, which was part of Mr Coucher's defence for not preparing the accounts in case of a fine. However, if Jarvis ever ended up in the dock it was always likely that Network Rail would join the company there, as it had established the safety rules.