Speaking at the Brand Republic Group’s Media360 conference, Tom Laranjo, the managing director of independent agency Total Media, said he was "surprised, actually, at the timing of the release, but actually not so surprised with the outcome".
"I think there have been whispers of it for a while," he added.
Also at the conference, Sam Diamond, the head of brand and comms at Gumtree.com, said: "I was most interested to see that the merger didn't happen because of cultural differences.
"It just goes to show that when you build up a big empire like that, you have a very specific way of doing things, all the people are sailing on the same ship going in one direction; it's very difficult to combine two companies."
None of the executives from agencies that are part of big holding groups agreed to be interviewed by Media Week.
Video produced by Georgina Brazier and Joel Fothergill