I have hidden nothing, Skilling tells Enron jury

The court was even shown the witness coaching firm's website, as prosecutors launched their crucial effort to undermine Mr Skilling's credibility and secure convictions on 28 counts of fraud and conspiracy.

During his first week on the stand, a humble Mr Skilling had painted Enron's bankruptcy as a tragedy triggered by Wall Street speculators.

However, prosecutors began their first day of cross-examination yesterday by painting Mr Skilling as a persuasive salesman whose word should not be trusted by the jury.

The aggressive questioning is being led by Sean Berkowitz, the director of the federal government's Enron task force, set up to investigate fraud at the energy company.

Enron's spectacular collapse into bankruptcy in 2001 shocked the financial world.

As the two Harvard graduates faced off, Mr Berkowitz asked: "You were well-rehearsed for making your testimony, right? And you are trying to convince the jury of something?" Mr Skilling said: "I have nothing to hide. I'm trying to describe what happened."

Enron was a house of cards built on greed and financial trickery, prosecutors allege, and the fraud that brought it down went right to the top. As the trial enters the crucial battle for the jury's sympathy, testimony has focused on share sales that are alleged to show how Mr Skilling knew that Enron was doomed to collapse.

Share sales that netted his ex-wife and fiancée more than $14m (£8m) in the run-up to Enron's bankruptcy were "a coincidence", Mr Skilling said. He also insisted that he sold $15.5m of Enron shares in September 2001, shortly after leaving the company, because of stock market turbulence in the wake of the 11 September attacks.

He said he had asked his broker to sell 200,000 shares on 6 September only in order to diversify his investments. He had quit the company the previous month.

Kenneth Lay, Enron's former chairman, is also due to take the stand in his defence. He is charged with six counts of fraud and conspiracy.