The founding partners, Nick Hurrell and Neil Dawson, now plan to recruit more creatives at creative director level, as they attempt to build a team with multidiscipline experience.
McIlrath, 43, joins the agency after a four-month break. He was previously at VCCP, which bought Heresy last year.
During his 23-year agency career, McIlrath has been seen as a leading light in creative integration within the UK. Hurrell said: "The fact that Shaun is so hard to categorise as a creative makes him ideal. He is fascinated by the kinds of ideas for which there are no award categories. That's why we have beaten down his door to persuade him to join."
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