Depends what you consider a serious assault. From what has been reported, it seems he only hit him once. However there was apparently a 20 minute period where he hurled abuse and told some who was effectively his junior that he was sacked. With the weight of petrol head opinion against him...
How on earth do you arrive at that 'theory'? The victim took himself to hospital. That, and the fact that Clarkson reported himself to the management suggests rather strongly that there was an assault. According to the BBC it only stopped following the intervention of a witness. James May...