Langdon is to head the new agency, Digital Marketing Group, as its chief executive.
The digital direct marketing business will be based in the UK and focus on both online and offline marketing.
It has secured funding through a reverse takeover with Seashell II, an investment company listed on the AIM 18 months ago.
The merger has raised £7.8m and the group has conditionally agreed to acquire two agencies: Dig For Fire, a direct marketing company with a digital element, and HSM, a digital marketing company.
Langdon said the acquisitions will form the "cornerstone" of the group, which he revealed was planning further acquisitions with the finance raised from the merger.
Langdon said: "We are delighted that both HSM and Dig For Fire share our vision for building an integrated digital direct marketing group. There are significant opportunities in the digital space."
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