He will report into David Fletcher, the chief data officer, to help the team support clients in understanding and adapting programmatic technologies.
At AppNexus, Beauchamp led new business in EMEA and worked with clients to develop ad tech solutions. He has also worked at nugg.ad and Net Communities.
Fletcher said: "Martin brings an engineering disposition and deep expertise of the supporting technologies to support all clients – from the most cautious to the most programmatically sophisticated – in getting the very most out of the emerging landscape."
Jason Dormieux, the joint-chief executive at MEC, said: "MEC is leading the charge through its data offering and I’m delighted to welcome Martin to the team, to assist our clients in navigating the complex programmatic landscape and ensuring their businesses thrive."