The merger is expected to be completed by May following recent clearance from the Office of Fair Trading, on condition Capital sells its East Midlands Century station.
GCap's commercial team is headed by the commercial director, Linda Smith.
Duncan George, the managing director of GWR's sales house Opus, will head GCap's national sales operation. John McGeogh, Capital's sales director, will keep the same role at GCap and Simon Dalglish, Classic FM's sales director, will fill the position of director of national brands and trade marketing. Linda Grant, Capital's national commercial director, left the company last week.
GCap Media will be the largest UK commercial radio operator, controlling around 40 per cent of the national radio advertising market, with a turnover in excess of £243 million from 55 analogue and 93 digital stations.
David Mansfield, the Capital chief executive, and Ralph Bernard, GWR's executive director, will take the same roles at the new company.