Pretorius, who will continue his technology chief role but with an expanded team, will now be responsible for growing the WPP group’s business, which spans Acceleration, Burrows, Cognifide, Fusepump, Possible (which was integrated into Wunderman in July), Salmon and Wunderman London.
While Pretorius's group-wide role is new, Wunderman has been without a UK chief executive since the resignation of Chris Perry, reported in Campaign in January 2016.
One of Pretorius's priorities will be to offer clients a seamless array of services across Wunderman’s constituent businesses, from digital strategy, events, ecommerce, content, marketing technology and digital consultancy.
Pretorius joined Wunderman in 2016 as chief technology officer as the result of its acquisition of Acceleration, which he founded in 1999.
Over the past three years, Wunderman has grown from 900 to more than 2,000 people, while new clients brought onboard include BT, EE and GSK.
Mel Edwards, Wunderman’s EMEA chief executive and chairman, said: "In the face of rapid change in digital marketing, clients are looking for simpler solutions spanning the full range of digital marketing.
"Stephan’s appointment is designed to support further collaboration and integration across our entire network of growing businesses in the UK."
Pretorius added: "This as an exciting opportunity to bring together a truly integrated digital experience offering underpinned by some of the best specialist resources available in the market.
"Wunderman UK is in a unique position to deliver the services businesses need to succeed in today’s digital economy."