Led by CEO Jeremy Sice, formerly head of digital and marketing agency SAS, it draws together a team of more than 220 from across the three agencies that form MSL Group's current UK offer.
The new structure includes an eight-strong cross-function board, with Capital MSL CEO Richard Campbell retaining his role leading the City offer and MSL London CEO Kelly Walsh made chief strategy officer.
The MSL London name will be dropped from January, with SAS and Capital MSL retaining their brand identity for the time being.
Below the board, the core of the business involves a 50-strong creative and production department staffed by the SAS team, alongside five planning and insight experts supported by 15 senior strategists.
This will sit alongside a 40 strong digital and social team and more than 100 PROs covering sectors ranging from financial and internal comms through to the corporate and consumer work offered by MSL London.
Sice said that drawing together of the three agencies, which has seen them sharing offices in London’s West End, followed more than two years of pre-planning.
"When it comes to a merger or an acquisition, you walk into a room and are told to start working together. To develop the best skills and best answers for clients you need to know, trust and be able to rate people, which two years has allowed us to do. You can’t do that in an M&A situation where you just tack a team on."
Claiming the move had not resulted in any job losses, he also pointed to the role of the creative team as core to the group’s offer.
"The key thing when tackling a client issue is about having an open-mindedness when it comes to considering creative possibilities. This is very different to bringing in a creative studio as an add-on – it will be about ensuring creativity, insight and content are there at the start of the process."
Sice declined to comment on whether the merger of Omnicom and Publicis, which owns MSL Group, had impacted on plans.