A chief executive officer (CEO) is often instrumental in the success of a company. Some CEOs will have spent several years at the same company, painstakingly climbing up the ladder. Some companies value long-term staffers in upper management and executive roles while others look to approach someone fresh from outside the firm. A recent study by BusinessFinancing.co.uk looked at which cities and countries across the world had the longest-serving CEOs, looking at the CVs of 100,000 CEOs around the world. Seven European cities made the top 20 listThe Greek city of Thessaloniki emerged in top plac…