WPP Group CEO Sir Martin Sorrell at Fox Studios on May 15 in New York City. Slaven Vlasic/Getty Images Snapchat has partnered with the world's largest advertising-agency holding group, WPP, and The Daily Mail to form a content-marketing agency, the companies announced Tuesday at a news conference at the Cannes Lions International Festival of Creativity.

The agency, Truffle Pig, will use Snapchat, the Daily Mail, and Elite Daily to test social content and marketing. The agency can work with WPP clients and other brands and plans to offer services such as positioning and messaging, content projects, video and photography, social-media management, audience development, and insights and analytics.

It will be led by WPP's Alexander Jutkowitz, managing partner of Group SJR. All three companies are equity owners.

We spoke to WPP CEO Sir Martin Sorrell at the Cannes Lions Festival of Creativity ahead of the announcement about what first appealed to him about Snapchat and how the deal came about.

Sorrell told us he first met Snapchat CEO Evan Spiegel in Chicago about six months ago, after an introduction from The Daily Mail US CEO Jon Steinberg.

Sorrell and Spiegel had lunch at Soho House. Spiegel was keen to sign up some of WPP's clients to sponsor the then-new Discover content section on the app, of which The Daily Mail is a content provider (alongside other brands such as Vice — in which WPP owns a stake — Cosmopolitan, and National Geographic.)

Sorrell acknowledged that he initially "insulted" Spiegel by accident: "I said, 'You're the only billionaire I know at the age of 25.' And he said: 'I'm 24.'" (He has since turned 25.)

Sorrell told us: "He was keen to get people to sponsor [Discover] at $750,000 a pop. Most of our clients said, 'Where's the data?'— so it was quite difficult to do that. I think his approach is very interesting, and we'll see."

The interest in forming a partnership with Snapchat is primarily around "developing social content," and Sorrell said WPP would help answer its clients' questions around data "to try to build a more substantiated model."

The appeal of Snapchat to WPP was around its unique, engaged user base of younger people.

Truffle Pig's launch at the Cannes Lions International Festival of Creativity 2015 on The Daily Mail Yacht. From left: Alexander Jutkowitz, Evan Spiegel, Jon Steinberg, and Sorrell. Lara O'Reilly/Business Insider

Sorrell said: "If you look at the data that our own futures group has produced, on the media habit of centennials — [people aged 0-18] — their attitude to Snapchat is markedly different from Facebook, so that seems to indicate generational changes ... Facebook is the largest country on the planet [in terms of users], but maybe centennials don't want that. They want 'Mission Impossible' [style] destruction. They want to keep stuff away from the prying eyes of others, family, and whatever else. But whatever the reason is, it's different. Therefore it's volatile. It indicates there's volatility, and it pays to be involved."

The Daily Mail's Steinberg recently compared Spiegel to a young Sorrell. We asked Sorrell whether he saw any of himself in Spiegel. He responded: "No, no — I wish I did!"

At the event Tuesday, Business Insider asked Spiegel whether he was concerned about what other agency holding groups may think about the launch of Truffle Pig — with the potential that Truffle Pig could use data from other agencies' Snapchat ad campaigns to inform and refine its own work.

Spiegel replied: "We are not worried."

Steinberg chipped in: "We are very collaborative by nature. Martin's agencies work with other agencies, holding companies ... if you want to do innovative stuff, you can't always worry about what people think."