The privately funded merger involved major shareholders, Australian telecom firm Telstra, Paul Ramsey Holdings, Publicitas and Andy McKelvey.

The two firms have been working together for some time to integrate print and broadcast ad delivery and asset management products and signed a Memorandum of Understanding in 2004.

The firm's managing director Andy Hopkinson (pictured) said the merger had been a "slightly complicated process", but that this had allowed for a smooth transition.

"It's given both teams a number of months to get to know each other. We've been managing this transition from a technical point of view for some time now. The businesses really complement each other," he said.

The global head office in Sydney has already been relocated to London, led by chief executive Gerard Barron, and Hopkinson said there had been no redundancies.

"Far from it. We're growing very fast. First-quarter results exceeded expectations and were significantly up from last year. We're hiring."

The 200-strong combined operation will be known as Adstream, and Hopkinson said it would continue to develop its cross-media, cross-continent range of digital ad delivery products.

He said growth areas included China, Japan and the US, with continued expansion across Europe.