The dispute centres on a multimillion-dollar deal allegedly “written on a napkin” and later formalised in writing.
Ian Rosenblatt, who worked as a business adviser for Mr Cowell from 2018, claims he is owed a percentage of a confidential deal made in 2025, under the terms of the agreement, and is seeking either payment or £100,000 in damages for breach of contract.
Mr Cowell, known for spotting talent on TV shows such as The X Factor and Britain’s Got Talent, is yet to file a defence to the claim.
Mr Rosenblatt helped with the transfer of shares in Mr Cowell’s company SyCo Entertainment, from Sir Philip Green and Sony to the former X Factor judge, leaving Mr Cowell with a 100% stake from July 2020.
Mr Rosenblatt was then appointed director of SyCo, but in late 2022 he wanted to quit.
Katherine Ratcliffe, representing Mr Rosenblatt, who is also a lawyer, said a month later, over dinner at Mr Cowell’s London home, the two men made an oral agreement about Mr Rosenblatt taking a percentage of a deal.
Ms Ratcliffe said: “By September 2022 Mr Rosenblatt intended to formally resign as director of Syco, and cease providing business advisory services to Mr Cowell, because of how challenging he had found working with Mr Cowell.”
She said it was “difficult to communicate” with Mr Cowell, who was “unpredictable” and “extremely emotional”.
Ms Ratcliffe added: “The terms of that offer were written on a napkin, which Mr Cowell then signed.”
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The handwritten agreement allegedly stated that Mr Rosenblatt would receive 8% of any deal over $30 million (£22 million), 10% over $50 million (£37 million), and 15% of any deal over $100 million (£74 million).
The napkin agreement was later written up and signed by Mr Cowell in February 2023 at his Cotswolds home, Ms Ratcliffe said.
Mr Rosenblatt claims he invoiced Mr Cowell in 2025, but has not been paid.
Ms Ratcliffe said: “In breach of the Dinner Agreement and/or the February 2023 Letter, the fee owed to Mr Rosenblatt has not been paid within 30 days of the date of the invoice or at all.”
A spokesperson for Mr Cowell declined to comment, the PA News Agency reports.
