Priest said: "It’s the ultimate approval of a great year so it’s a great feeling."
In an interview with Campaign, the four founding partners, who also include James Murphy, David Golding and Jon Forsyth, said the accolade recognises the whole agency, not just the creative or strategic side.
Priest said: "We get creative awards throughout the year, we have effectiveness awards, but this takes in those, new business, how we’re expanding and growing the company, and the different divisions that we’re setting up.
"This recognises the agency’s output in its entirety and it’s for everyone in the agency."
Golding, who is also the chief strategic officer, highlighted the importance of winning the award.
He said: "It’s famously rigorous, it’s famously well thought through. You have to earn it and win it on merit, and being good across many things. It’s the ultimate challenge."