Peter Johnston, an Antrim-born entrepreneur who has raised money from some of the world’s most prominent tech investors, is in the process of building a new start-up, The Currency understands. Johnston started out as a designer for advertising behemoth M&C Saatchi in London in May 2011 before joining Google a year later. Since then, he’s gone on to set up numerous tech start-ups that have won investment from the likes of Peter Thiel, the Collison brothers, US venture capital giant Andreessen Horowitz, and Reddit co-founder Alexis Ohanian. The Carrickfergus native is now a co-founder of Profile.com, a San Francisco-based business…