Leendert obtained a Masters in Psychology at the University of Amsterdam 1975.

His professional life started as Project Manager for the Research Institute for Applied Psychology, and from there:

1980 to 1991: Media Research director of Dutch Research Agency Intomart.

1991 to 2010: Joint Managing Director of what later became Intomart GfK.

2001 to 2013: Managing Director of the Intomart GfK Group in Belgium and the Netherlands.

He was a member of the Media Board of GfK, a member of the Steering committee for ad hoc research of GfK and, among others, also a member of the GfK Custom Research Board of Western Europe.

Next to his responsibilities with GfK , he is former president of the MWG (connecting media professionals)  in the Netherlands and past president of SPOT,  the Foundation for the Promotion and Optimisation of Research on Television Advertising in the Netherlands.

Leendert was managing director of the Intomart GfK group, with companies like

In the Netherlands:

• Intomart GfK
• Adware Media Solutions,
• Jan Schipper Company
• GfK Daphne
• And in Belgium:
• GfK Audimetrie
• Sygnificant GfK

He is a well known presenter on:

• Esomar Conferences, including the WM3 Esomar/ARF conferences,
• Print  & Digital Research Forum (formally known as World Wide Readership Research Symposium)
• ASI conferences
• SAARF conferences

His experience in his working life includes having being a member of several company boards in the Netherlands and Belgium, so he is a skilled expert in Corporate Governance.

He was involved as project leader or as member of acquisition committees in several Merger and Acquisition processes.