The Weber Shandwick CEO took his seat alongside presenter David Dimbleby, former Daily Mirror editor Piers Morgan, trade and industry minister Margaret Hodge, shadow trade and industry spokesman Alan Duncan, and co-leader of the Green Party Sian Berry.
Rival agency chief, Edelman president and CEO David Brain, was quick to praise Byrne's 'bravura performance'.
Brain, a friend and former colleague, adds: 'Colin out-soundbited a government minister and a shadow minister, and accused one of Britain's best-ever tabloid editors of being middle class. How refreshing.'
In publicity terms, last week also went well for another of the industry's big-hitters, Brunswick founder Alan Parker.
Using his wedding as a hook, a profile in The Sunday Times hailed 'the kingmaker keeping court with Brown and Cameron'.