Lawrence (pictured) will continue to be new business lead and senior counsel across a portfolio of accounts.
He has 25 years' experience leading UK and international campaigns, including a 16-year tenure with Weber Shandwick.
"It's a great honour to take on this role at a truly amazing agency with a fantastic team and brilliant clients," said Lawrence.
He will be responsible for day-to-day agency management and growth, reporting to chief executive and founder Gay Bell.
Bell said the agency had gone from strength to strength since Lawrence joined in 2017, winning 15 new clients, and expanding the agency's integrated offering.
"Altogether, the agency has grown by almost a quarter each year. I'm delighted that David is stepping into this new role and excited to continue to work closely with him as we develop Platform," she added.
The agency has recently delivered global campaigns for clients including Bitmovin, The Switch and Verizon Media.