* Conviction provides ammunition for future cases * Shareholders anxious for closure By Andrew Callus LONDON, Nov 16 (Reuters) - BP stands convicted of the biggest corporate crime in U.S. history, based on the scale of its punishment. Moving on will not be easy. Having agreed to pay $4.5 billion and wear the label of felon, the British oil company will face no further federal criminal charges over the 2010 oil spill disaster. On the downside, lawyers now have extra ammunition for civil processes that could cost a great deal more. And as a company convicted of criminal acts, BP could be suspended or debarred from contracting with the federal government in a country that represents about a quarter of its business. BP's shareholders have watched the company shrink before their eyes in the two and a half years since the Deepwater Horizon rig exploded, killing 11 people and spewing crude into the ocean for three months until the mile-deep Macondo well was capped. These days, closure is what they crave. "BP are inching ever closer to drawing a line under the Macondo incident and I think that investors will be happy to have some finality, even if it does mean a headline grabbing fine," said one top 15 investor as details of the settlement emerged on Thursday. Analysts on a conference call tried to coax some positive statements from finance director Brian Gilvary and the company's top lawyer Rupert Bondy about the mountain BP still has to climb, but both men stuck to their cautious script and gave no guarantees on what happens next. Total balance sheet provisions for the spill rise to $42 billion from $38 billion as a result of Thursday's ruling. That's about a third of the equity value of the company itself, and well over a year's worth of capital investment spending. But based on a rough calculation of estimates from analysts and some previously paid items, BP's total bill from the spill could exceed $58 billion. BP has raised $35 billion through the sale of assets and has paid out, or is preparing to pay out, roughly the same amount. But everybody expects BP to pay more yet. The question is how much more. Clean Water Act legislation is one of the few quantifiable areas. Based on an estimate of 4.9 million barrels spilled and a maximum fine of $4,300 per barrel. BP could pay $21 billion if it is found guilty of gross negligence at a trial that begins in February. BP, arguing that it is "no more than negligent", has earmarked only $3.5 billion and says it would appeal against gross negligence. Alabama Attorney General Luther Strange, who represents other states hit by the spill, said on Thursday he would pursue a finding of gross negligence. Analyst Richard Griffith of Oriel Oil & Gas said Thursday's announcement was "a material step forward for BP in terms of removing another uncertainty." "Nevertheless, the civil trial could still be long and protracted with the risk of a gross negligence verdict that would be appealed," he said. Finance director Gilvary also conceded on Thursday that should it be debarred from operating in the United States, BP would have to kick off another major rethink of strategy. "BP has not been advised of the intention of any federal agency to suspend or debar the company in connection with this plea agreement," was all the reassurance the company could give.