MARK MOODY-STUART is not saying anything. As the man at the top when Royal Dutch/Shell was busily overbooking its proven oil reserves, he has kept his mouth firmly shut, preferring to bury himself in his role as chairman of Anglo-American.

So has Judy Boynton, the finance director, who since she joined in 2003 has signed off the accounts when the figures for oil reserves — a key measure of the company’s profitability — were clearly wrong.

And what of Lord Oxburgh, the senior non-executive director who was promoted to the role of interim non-executive chairman? Where has he been while the problems surrounding Shell have threatened to engulf the business? They have been nowhere to be seen. And yet all three could now face questioning as the finger of blame points at yet more targets.

While the US Securities and Exchange Commission (SEC) moves ever closer to ending its review of Shell’s bookings, and US class-action lawyers put the finishing touches to their lawsuits, the shutters at London’s Shell Centre have come down.

On March 3 it almost looked as if the oil giant had got the message. Sir Philip Watts, the chairman, and Walter van de Vijver, the head of exploration and production, had been forced to resign, and the shares rallied on the back of expectations of change.

The company issued reassuring statements that a working group set up to find out how Shell managed to overbook its proven reserves by 20% had discovered no illegal activity in the conduct of management.

The market was eager to give the company the benefit of the doubt. After all, with Watts and Van de Vijver gone, greater transparency and communication must be on the way. Surely it was only a matter of time before Shell would do away with the cumbersome Anglo-Dutch dual board structure? The subsequent conference call with the new chairman of the board, Jeroen van der Veer, changed all that. He was unwilling to confirm even that illegal activity had taken place or that there would be any changes to the structure of the company before 2005, and as a result the shares tumbled again.

As one analyst said: “The conference call raised more questions than it answered.”

Despite Shell’s fearsome hold on its dealings with the media, damaging leaks have come to light that Shell executives, including Boynton and Van der Veer, knew about the reserves issue as far back as 2002. Their jobs remain under threat. Internal documents allege that Shell releaxed accounting guidelines used to book reserves. Then the SEC confirmed it was looking at Shell’s global bonus structures. A statement issued by Aad Jacobs, head of the audit committee, designed to support the group’s senior management, did not improve sentiment.

One source familiar with Shell’s bonus scheme insisted that nobody’s pay had been greatly boosted by the reserves. A complex arrangement based on “scorecards” sets the criteria for bonuses. Reserves replacement does not even appear on the list for senior management, and it is only one of a number of criteria for those in exploration and production (E&P).

“Within E&P it had a single-digit percentage weighting, so a typical senior E&P executive may have received 5% of his or her bonus based on reserves replacement,” the source said.

Yet the message did not get through. Fadel Gheit, oil analyst at Oppenheimer in New York, believes that Shell is in denial. He said the firm had placed too much emphasis on getting rid of Watts and Van de Vijver, and more needed to be done.

“The focus has been on the individual, and the latest one to be brought back into the picture is Moody-Stuart. How long did the overbooking go on? Shell needs to get to the bottom of this issue. It has dug itself into a hole,” Gheit said.

Rival oil companies agree. One insider said the industry was furious that Shell had caused the market to lose confidence in the sector. “Everyone’s looking for signs that we’re up to no good,” he said. BP, for example, started to buy back shares to bolster the share price but has had little success.

More bad news could be on its way because the working group at Shell is due to report within weeks. Shareholders are due to meet Oxburgh shortly and he will be under severe pressure to confirm the permanent appointment of an outsider as non-executive chairman.

There are a few scraps of comfort. The signs are that the reserves numbers will not change, at least dramatically, when the group publishes its findings. Shareholders on this side of the Atlantic also appear to be rejecting American law firms keen to sign them up to class actions.

And while some Americans are gearing up to sue, others are buying in. Capital Group, one of the world’s largest investment companies, has bought up more than 280m shares, making it now a top 10 shareholder in Shell Transport and Trading, the London-listed business.

Some at least, see Shell as a buying opportunity.