Manifest Group, which has 25 staff in London and five in New York, was legally created last week and is fully owned by Myers.
Myers previously owned 51 per cent of Manifest London - which was the UK's 122nd largest PR firm in 2015 and in turn owned Manifest New York. Myers founded the London agency in 2009.
The rest of Manifest London was owned by Nev Ridley and Shaun Beaumont, friends of Myers who had set up Manchester and Leeds integrated agency Manifest Communications in 1999. Forms confirming the immediate transfer of shares were submitted to Companies House last week.
The Manchester and Leeds business is now known as ilk agency, and will open a London office on 1 August.
Meanwhile, Manifest Group is looking to execute Myers' aim of having five global offices by opening in Cape Town "within the next 12 months", he told PRWeek.
Myers said that South Africa was an attractive prospect due to low cost of investment, its growing market and the fact that "having a foothold in Africa is increasingly important for some of our global clients".
He told PRWeek that he did not want Manifest to "get to such a scale in London that it affects our agility" - saying that he had previously assumed this would be the 30-staff mark, but that he now felt a higher level was sustainable.
Myers said the split with what is now ilk had been "very amicable", adding he was keen to have full control of the Manifest brand and allow both brands to grow in their own way.
Ridley said: "It was exciting to join forces with Alex in London in 2009 and to help launch the Manifest London business, but the time has come to let Alex take his agency where he wants to go, and for us to concentrate on the continued growth and evolution of ilk as a leading integrated agency in the UK."