Henderson would become CEO of the ill-fated combined business, while Vivian remained as a partner but left at the end of last year. Vivian held the roles of partner in the firm's financial and corporate division and MD of its geopolitical business.
Vivian has now taken the role of financial and corporate director at Tavistock Communications. He is in discussions about taking a stake in the business.
In the summer, Tavistock signed a collaboration partnership with Weber Shandwick. Tavistock's financial clients include property investor Hansteen, mining business Gemfields and telco company Zegona. The corporate roster includes Rolls-Royce, developer Hammerson's development in London's Brent Cross and German defence manufacturer Rheinmetall.
Vivian told PRWeek that he and Tavistock CEO Jos Simson had been "friendly competitors" previously, with the pair in particular competition within the mining and resources business, which was one of Pelham's strongest areas. Vivian said: "This is an exciting time at Tavistock and I very am pleased to be part of a growing business that has advanced plans to develop in the UK and internationally."
Tavistock is based at City offices in 1 Cornhill - the same building in which Pelham was initially established.