James Murphy, founder and CEO of adam&eveDDB and Karen Blackett, chairwoman of MediaCom UK & Ireland spoke in support of the motion, while Rory Sutherland, vice-chairman of Ogilvy Group UK and John Billett, chairman of ID Comms, opposed it.

Murphy talked about the impact of Brexit on jobs in advertising and client confidence. “How long before Unilever is enticed to become more Dutch?” he asked as he talked about how damaging Brexit was for “brand Britain”. Among fellow US CEOs he said there was “neither fire nor fury, just pity for what we had done”.

In retort, Sutherland argued that advertising would be affected “less than most” by Brexit and that as an industry, people should “only worry about the things we can do something about”. He also claimed that “extra foreign competition would do us good”.

In terms of hiring talent, he argued that leaving Brexit might make it easier and that the European Freedom of Movement was “slightly racist in nature”.

But his over-riding argument against the motion was that advertising faced far greater challenges, not least the commoditisation of the industry; the obsession with chasing short-term metrics; and the erosion of trust.

Blackett countered that the reason Brexit was the ad industry’s biggest challenge was because – unlike the other challenges it faced such as automation, trust and brand safety – it is “not in our control”.

“It has changed client behaviour. If we can’t persuade our clients to invest in brand building in the long term, we won’t have a job,” she said. At MediaCom-owner, WPP,  15% of talent across its agencies was from the EU but that now “we now longer look like a welcoming country”.

Billett talked about the wider challenges facing advertising including fewer brands, the rise of ad-free subscription media, reducing audience to ad-funded media and the dominance of Google and Facebook in online advertising.

After questions and comments from the floor, Sutherland and Murphy summed up.

Sutherland said: “As a behavioural science nut, to speak of it as though leaving is a risk and staying in is a no-risk option – that’s a bias. Complexity physicists would argue that the most dangerous system is one with no capacity for self-correction.”

But ultimately his argument centred on Brexit not being as big a challenge for the advertisign industry as the erosion of trust.

Murphy summed up saying: “We are a creative and dynamic industry and we can deal with trust issues – they are being dealt with…Brexit is an ‘unknown, unknown’, there are no rules for this situation, no one has left before.”

The motion was defeated – 37 supported it, 56 opposed it.