Global Infrastructure Partners (GIP), the world's largest infrastructure-focused private equity firm, bought Gatwick Airport from Ferrovial-owned BAA for £1.51bn in November 2009, using Bell Pottinger Corporate and Financial to support the high profile deal.
Former BPC&F deputy chairman Charles Cook headed the account at the agency and GIP has followed him to Merlin PR, which he joined as a director last month after his former agency's merger with Pelham.
The agency will report to Jack Cowell, GIP's director of marketing in New York, who confirmed that Merlin would take responsibility for the 'systematic management of our media relations and public relations efforts, based in or near the UK'.
The focus of Merlin's work will be targeting and influencing key opinion-forming media and providing deal support.
The retainer account will be topped up by project fees as the firm continues to invest in non-US assets.
Recent media reports suggest that the firm, founded by Credit Suisse and General Electric, is planning to launch a further $5bn (£3.34bn) fund to enable it to acquire more infrastructure assets.
It is thought discussions have already started with existing and potential investors ahead of a launch in the second half of the year.
GIP has attracted heavy-hitting partners this year, having sold a 15 per cent stake in Gatwick to the Abu Dhabi Investment Authority, the world's largest sovereign wealth fund, for £125m in February.
That sale came days after the South Korean National Pension Service bought a 12 per cent stake in the airport for £100m.
The UK remains a key market for GIP as, in addition to Gatwick and London City airports, it owns the Port of Great Yarmouth and Biffa, the waste management business.
GIP is thought to be eyeing European assets, as debt-laden nations may see the private sector as an ideal way of raising funds and rejuvenating infrastructure assets.