The agency, which opens its doors this week, has secured three founding clients in the fashion retailer New Look, the shirt-maker Charles Tyrwhitt and the US technology company Sling Media.
The direct agency Kitcatt Nohr Alexander Shaw has taken a minority stake in Trinity, which will be based at the offices of Miles Calcraft Briginshaw Duffy. However, MCBD will not have a financial interest in the start-up.
Trinity will work on planning across digital, brand and direct. Nunn is a former managing partner of Manning Gottlieb OMD, Lennox headed OMD Group's digital business and Timlett is a former managing partner of Brand Connection and director of Optimedia.
The founders said Trinity's aim is to offer "unified media planning" and it will oversee buying across all channels with media buying agencies. However, it will stop short of handling any buying itself.