London Briefing: It was all so different a year ago: Lord John Browne of Madingley, chief executive of BP, had just been voted Britain's most impressive businessmen for the sixth year running, and was looking forward to extending his lengthy reign at the top of the world's second-largest oil producer.

Yesterday, speaking via video-link to Houston, Texas, he accepted the damning indictment into BP's corporate safety culture that was delivered in the long-awaited Baker report.

Headed by former US secretary of state James Baker, the investigation into safety at BP followed the Texas city refinery disaster in 2005 in which 15 people were killed and hundreds injured. It was America's worst industrial accident in a decade and BP is now paying a heavy price, not just in financial terms but also in terms of its reputation.

In financial terms, the Texas explosion has cost BP some $2 billion (€1.5 billion) in compensation payouts and repair costs. It has also set aside as much as $1.6 billion to cover legal disputes and has stepped up safety spending on the Texas site and elsewhere in its global empire.

The 374-page report highlights serious safety issues at all five of the group's US refineries, noting a lack of operating disciplines and apparent complacency.

So while the news that Browne is to quit the oil group 18 months ahead of schedule shocked the London stock market last week, the reasons behind his early exit are now crystal clear.

BP got first sight of the report last Wednesday, two days before Browne announced his departure in a late-afternoon announcement on Friday.

Claims from some BP insiders that the two events were unconnected stretched credulity and there are few who do not believe that the BP boss jumped before he was pushed.

Gallingly for the man dubbed the "Sun King", BP shares responded to news of his departure last Friday by jumping almost 2 per cent in value.

His early exit is all the more ignominious given that, just a few months earlier, Browne had fought a bitter battle over his retirement date with the BP chairman, former Irish attorney general Peter Sutherland. In a compromise deal, it was agreed that he would stay on until the end of 2008, rather than departing when he turns 60 in February next year.

Litigation-happy lawyers in the US are certain to seize on the report's findings and the widespread criticism that the group sacrificed safety to cost-cutting. The grand jury in the US is still investigating whether to bring criminal charges, while BP also faces action on its Alaska spill.

Handling the fallout will be a massive test for Browne's successor, BP's 49-year-old head of exploration and production, Tony Hayward, who formally takes over as chief executive when Browne leaves in July.

Hayward is understood to have been Browne's top choice from a list of internal candidates for the job. Indeed, some insiders suggest that the chance to anoint his own successor was a key factor in Browne's decision to leave early.

As criticism of the BP boss mounted following the row over his retirement, his authority came under threat. Had he stayed on to the end, he might have found other, more powerful boardroom voices promoting their own proteges for the top job.

Although a BP "lifer", the youthful-looking Hayward had, even before news of his elevation, been attempting to distance himself from the old regime, criticising the culture of an organisation that "doesn't listen" and a management style that "makes a virtue of doing more for less".

If that is the new chief executive's view of BP, then how will history view the legacy of Browne, particularly in the light of the Baker report and the catalogue of disasters that prompted it?

He has undoubtedly been one of Britain's most brilliant businessmen; a truly global player admired not only at home but also on the world stage. In his 40-year career at BP, he transformed the group from an also-ran in the energy industry into its second-most powerful player.

But the accusations of systemic failures at the group have led to a reappraisal of what had, until recently, been the most glittering of careers.

Just how quickly his successor can achieve rehabilitation for the group is likely to be a crucial element in how harshly corporate history will judge the outgoing BP boss.

Browne's reputation remains sufficiently intact for him to be able to walk into a top job in almost any other company, although it is thought he might take on a role in the arts, his other love apart from the oil industry. He already has a role at a private equity firm, Apax.

And, as always in British industry, his departure will be cushioned by lucrative financial arrangements.

BP's performance means he might well miss out on full bonus payments this year, but he is sitting on shares worth as much as £12 million (€18 million) and has a massive pension pot of £20 million, one of the biggest ever seen in a British boardroom, and from which he will reap an annual payment of more than £1 million.