A High Court judge in London has reserved his ruling on a case that could lead to Bernie Ecclestone losing control of Formula One racing.
Bernie Ecclestone's grip on Formula One is being challenged
Three creditor banks have disputed the make-up of the board of Formula One Holdings (FOH), the company that runs the Grand Prix circuit.
Mr Ecclestone's family trust firm has a majority on the FOH board, despite only owning 25% of its parent firm.
The judge said he would hand down his judgement later in the year.
FOH has indicated that it will abide by any decision of the court.
At stake is Mr Ecclestone's grip over a sport from which he has amassed a reputed fortune of £2.3bn ($4.2bn).
He started the F1 revolution in the 1980s by persuading team owners that he should negotiate on their behalf for television and marketing rights.
Bayerische Landesbank, JP Morgan and Lehman Brothers are creditors to bankrupt German media group Kirch, which had acquired 75% of Slec, FOH's parent company.
Mr Ecclestone's family trust company Bambino Holdings owns 25% of Slec but controls FOH through a right to appoint subsidiary directors to the board, the court heard.
The banks, known collectively as Speed Investments, are disputing the appointment by Bambino of two directors to FOH in 2002 in a bid to gain a majority on the board.
Elizabeth Jones QC, the lawyer for the banks, asked the High Court to formally rule that there was "no defence" to their challenge that the appointments were "invalid".
The case could have a bearing on the dispute between Ecclestone and the car manufacturers involved in F1.
The car companies have threatened to set up a rival series in 2008 if they are not given a bigger share of F1's revenues and more say in the running of the sport.