Willem is a Dutch eXtreme Programming pioneer. Since 1999 he guides organisations in being more effective, often through the introduction of Agile Software development as an all-hands person: coach, developer and facilitator. Always active in the local and international community, he serves as host of systemsthinking.net and the European Agile Open conferences and previously on the Agile Alliance board and co-founder of XP Days Benelux. Willem is an appreciated workshop facilitator at practitioners' conferences like XP(Day), Software Practice Advancement and Agile200*.

Willem is a partner in QWAN (Quality Without A Name), an initiative of pragmatic practitioners, who have joined forces to deliver courses and mentoring on effective software development.