Travers Smith and Locke Lord are advising on Sir Martin Sorrell's new business venture, following his resignation as CEO of advertising agency WPP earlier this year.

Sorrell (pictured) and his investment vehicle S4 Capital Limited are being advised by Travers on the creation of a new company, S4 Capital, including its £51m fundraising and reverse acquisition by investment firm Derriston Capital.

Upon completion of the deal, S4 Capital will replace the Derriston brand, with Sorrell taking the helm as executive chairman.

Travers corporate partner Aaron Stocks is leading the firm's team advising, which also includes tax partners Jessica Kemp and Kathleen Russ.

Derriston is being advised by US firm Locke Lord, with London managing partner James Channo and corporate senior counsel Nicholas Jennings acting.

Sorrell stepped down as CEO of FTSE 100 advertising agency WPP in April amid misconduct allegations, with Allen & Overy (A&O) and Slaughter and May brought in to advise the company over the claims. A&O litigation head and employment partner Karen Seward is understood to be taking a lead role for her firm.

Quinn Emanuel Urquhart & Sullivan London co-managing partners Sue Prevezer QC and Richard East are advising Sorrell, alongside employment specialist firm Lewis Silkin.

WPP also appointed Wilmer Cutler Pickering Hale and Dorr to independently investigate the allegations. It is understood that London-based litigation and investigations partner Stephen Pollard is leading the US law firm's team.

The probe, first reported by The Wall Street Journal, relates to claims of personal misconduct and possible misuse of assets by Sorrell – allegations he has denied.