Ross Mendham, 41, pleaded guilty to assault and possession of a Class A drug after he punched an assistant manager at the Ivy restaurant in Norwich on July 22, Norwich Magistrates' Court was told. Magistrates fined Mendham £373 and ordered him to pay £282 in costs.

Prosecutor Stuart Cowen told the court that restaurant staff had attempted to restrain Mendham when he lashed out, striking assistant manager Connor Humpleby with a single blow. Police were called to the scene and, while Mendham was being removed after his arrest, officers noticed a small plastic bag containing a white powder fall to the floor and seized it. Mendham admitted possession of cocaine and the assault.

David Foulkes, defending, told the court that Mendham had been dining alone and became aggrieved over what he "felt was poor service". Foulkes said Mendham was "very sorry to the person he struck." The Crown did not seek a custodial sentence for the offence reported to the magistrates.

Mendham appeared on the BBC programme Dragons' Den in 2013, securing a £60,000 investment from entrepreneur Peter Jones for Barenaked Foods, a business that produced low-calorie and low-carbohydrate pasta, rice and noodles made from konjac. The firm's products later appeared in several major supermarkets, including Waitrose, Sainsbury's, Tesco and Morrisons. The court was told Mendham continues to receive thousands of pounds each month as a director of the company, although he is no longer involved in its day-to-day running.

Last year Mendham launched a fashion brand called God of Design that upcycles vintage and designer clothing. He is the son of former Norwich City footballer Peter Mendham. In March of the previous year Mendham was a passenger when a Ferrari F430 crashed on Rose Lane in Norwich city centre; the driver, Joey Baptiste, was later fined after admitting careless driving.

The case adds to a record of incidents involving public figures who have appeared on national television, and it concludes with a financial penalty and costs rather than a custodial sentence. The court's penalty reflected the admitted offences and the circumstances described by both prosecution and defence at the magistrates' hearing.