One of Britain's biggest fraud trials - and certainly one of the most keenly awaited gets on underway today.
HP is suing one of Britain's best known tech entrepreneurs, Mike Lynch.
HP bought Mr Lynch's company Autonomy in 2011 for $10bn - it is suing him for $5bn, saying he and his chief financial officer over-inflated its value - in essence by false accounting.
"It sold itself to the stock market as a purely software company, but according to HP it was reportedly selling computers and laptops from other companies at a loss, purely to get those quarterly revenue figures - which the market and HP were looking at - up," BBC technology correspondent Rory Cellan-Jones told Today.
On Friday, new criminal charges of securities fraud were laid against Mr Lynch by US prosecutors.
Mr Lynch has consistently denied all the charges made against him - he alleges that HP ran Autonomy into the ground through mismanagement.