The media planning and buying agency will be co-founded by Mills with former Carat marketing director Jenny Biggam, who also left Carat shortly after Mills quit as MD in January after 11 years with the agency.
A website for the agency, The7Stars.co.uk, went live today (Weds), around 14 hours earlier than previously planned.
Earlier this week the site displayed a clock counting down to 9am on the morning of Thursday 1 September.
The7Stars has already named two of its partner companies in the project - BLM's digital division, Quantum, and Media Week Award winners for 2002 and 2003, strategic communications outfit Naked.
In an introduction to the agency, the website claims: “The7Stars is all about individuals that make a real difference to their clients’ business. Processes and structures do not make a difference to clients' business – people do.
“We aim to attract brilliant people in the media industry to work with us by creating more rewarding roles and a working environment that inspires everyone.
“The clients who will enjoy working with The7Stars are those who value the highest levels of personal service; creative and innovative thinking, and the best people in the business working on their account.”
Carat’s former head of media, Mark Jarvis, will also complete the triumvirate of former Carat staffers in the new venture, though he is still on gardening leave after quitting the Aegis owned agency in June
Jarvis quit the agency after weeks of speculation about his future.
The head of media was reported to be leaving the agency for a secondment to gaming client Gizmondo, although he then pledged his future to the agency and remained in the same role.
However, within weeks Jarvis performed an about face and left the agency, fuelling speculation he would reunite with Mills and Biggam on a media-related project.
At Carat the trio represented what was a formidable force in UK agency circles.
They helped propel the Aegis-owned outfit up the league tables of billings as it formed a considerable reputation as one of the hottest buying shops in the business.
Carat commercial director Neil Jones replaced Mills as managing director of the agency.
By James Livesley and Kevin May
This article was first published on Media Week