Serial entrepreneur Mark Roden (57) recently took back the reins at Ding, a provider of mobile phone top-ups for over 400 operators in 130 countries. Roden told the Sunday Independent that it has ambitions to hit 500,000 monthly active users by 2020. He started the company - which has revenues of $500m (€440m) a year - based on a conversation he had with an Indian waiter in Dubai 13 years ago. He plans to raise over €50m for the company in the coming months, From Dublin, Roden dropped out of dentistry in Trinity after a year and went to work for Denis O'Brien, helping start up Esat. He is also an angel investor and peer-to-peer lender.