The move marks S4’s second acquisition following the merger with Dutch digital agency MediaMonks earlier this year.

Sorrell formed S4 Capital following a reverse takeover of Derriston Capital after departing from his position as chief executive of WPP earlier this year.

San Francisco-headquartered MightyHive increased its revenue at a compound annual growth rate of 129% from 2015 to 2017, S4 said in a statement.

As part of the acquisition agreement, Peter Kim and Christopher Martin, chief executive and chief operating officer of MightyHive respectively, have been appointed as directors of S4 Capital.

MediaMonks founders Victor Knaap and Wesley ter Haar, alongside chief financial officer Peter Rademaker, will also become directors.

S4 plans to offer digital marketing services in three initial areas: the development of a global digital content platform; digital media planning and creative ideas based on first-party data; and digital media buying.

Sorrell, executive chairman at S4 Capital, said: "The merger with MightyHive marks an important second strategic step for S4 Capital. MediaMonks’ award-winning digital creative production and MightyHive’s market-leading programmatic offering will give S4 Capital’s clients end-to-end, fully integrated and seamless capabilities in purely digital marketing.”

He added that the company will be organised primarily on a “unitary basis”, with key figures within the business “incentivised through significant, equity ownership in the enterprise as a whole”.