Three executives who sold their company to S4 Capital are suing the agency group helmed by advertising mogul Martin Sorrell, alleging it has withheld millions of dollars and shares owed to them.
The former CitrusByte execs allege in the lawsuit that S4 engaged “in a campaign of obfuscation and delay” and raised “unfounded claims and arguments” to avoid payment, allegedly withholding at least $7 million in escrow funds and delaying or withholding millions of S4 shares tied to the deal.
S4 declined to comment on ongoing litigation. The company has not made a legal response to the claims in the lawsuit, which was filed earlier this month.
UK-based S4 was launched in 2018 by Sorrell, following his acrimonious exit from WPP, where he had served as CEO for more than 30 years. The company, which focuses on digital marketing, grew in size rapidly through more than 20 acquisitions in its early years.
S4 acquired CitrusByte, a tech consulting firm later known as TheoremOne, in 2022. It sits within S4’s Monks Technology Services division.
The lawsuit highlights the friction in Sorrell’s empire-building strategy, in which S4 typically acquires agencies and tech businesses for a mix of cash, stock, and future earnouts. A public court battle risks creating a distraction and could complicate future deals at a time when it’s trying to turn around its business.
S4’s rapid expansion in its first four years was followed by a more difficult period, as major tech clients cut marketing spending and some of its agencies underperformed.
The company has since been focusing on reducing its costs, including cutting its head count to 6,150 as of June this year, down from more than 9,000 at its largest. S4 Capital’s stock has fallen by around 94% since its 2021 peak. Its market capitalization stands at about 347 million pounds, around $470 million.
The complaint, filed in Delaware Superior Court this month, was brought by Brady Brim-DeForest, CitrusByte’s former CEO; William Jessup, who was previously the firm’s head of services delivery; and David Kullmann, its former head of staffing.
The lawsuit says that a year after the transaction closed, S4 said CitrusByte had met the standards required by its purchase agreement and agreed to make a “maximum contingent payment” to the CitrusByte security holders. The exact details are redacted in the filing.
The lawsuit alleges that S4 has refused to release at least $7 million held in escrow accounts after anniversary payout deadlines in 2025 and 2026.
S4 said it had the right to withhold the money to cover costs related to a separate legal dispute with a former CitrusByte executive, Yoav Cohen, the lawsuit says.
Cohen served as chief commercial officer of S4’s Formula.Monks tech services division after S4’s CitrusByte acquisition. He sued S4 and CitrusByte in March 2025, alleging they had failed to pay him two-thirds of $940,000 in incentive payments owed following a settlement. A week later, the parties agreed to dismiss the case with prejudice, meaning that the same claim can’t be refiled.
Brim-DeForest, Jessup, and Kullmann countered that the Cohen matter arose after the deal closed, arguing the deal’s contract only made them financially responsible for liabilities created before S4 took ownership. Brim-DeForest, Jessup, and Kullmann also allege that S4 settled Cohen’s claim without obtaining their contractually required consent, which they argue meant that they were off the hook for costs associated with the dispute.
The suit also claims S4 didn’t deliver shares in a timely manner that were due to the executives in 2025. It says S4 did eventually issue the shares owed to Jessup and Kullmann in November that year, but hasn’t released the shares owed to Brim-DeForest.
The former CitrusByte executives are seeking at least $7 million in cash payouts related to the escrow accounts, damages for the withheld and delayed equity, and legal costs.
