Bellens started his career in 1978 as an
auditor at
Deloitte Haskins & Sells. During his time at Deloitte he was engaged on the audits of the Belgian subsidiary of
General Motors. In 1981 he became financial director of the
Compagnie Brussel Lambert holding (GBL). He managed the investment portfolio and prospected potential investments. He became Deputy Manager of the
Pargesa Holding in
Geneva in 1985, where he was responsible for the management of holdings, mergers and acquisitions. Didier Bellens managed the participations of the GBL group in the company. In 1992 Didier Bellens came back to the
Groupe Bruxelles Lambert as Managing Director, taking charge of the group's strategic participations in companies such as
Royale Belge, the BBL, and the CLT. He played an instrumental role in the merger between AXA and Royale Belge, and the change and the negotiations leading to the
merger between CLT (
Compagnie Luxembourgeoise de Télédiffusion) and UFA. He also participated in the exchange of shares between RTL and
Bertelsmann, which gave RTL a minority participation in Bertelsmann, and the change of ownership of the BBL. He joined the RTL Group in 2001, which was created through the merger of CTL-UFA and
Pearson Television (now FremantleMedia), as its
CEO, where he focused on the group's international expansion. He concluded the merger with Pearson Television and launched the RTL Group on the stock market. In March 2003, Didier Bellens was appointed Belgacom's president and
chief executive officer as the successor to
John J. Goossens. In March 2009 his mandate at Belgacom was renewed in March for a six-year term. His position at the head of Belgacom almost ended in 2011 after a strong dispute with the company board and the Belgian federal minister for Civil Service and Public Enterprises,
Inge Vervotte. After a few incidents (accusation of conflict of interest, derogatory comments about the government, alleged covert promotion of confidante) the government decided in 2013 the relationship of trust was seriously damaged and Didier Bellens' position was no longer justifiable. He was dismissed on the basis of serious professional misconduct. ==Other activities==