How did Emotion-Focused Therapy (EFT) come about?

In this video, Les Greenberg explains how his studies of how people change in psychotherapy led him to develop Emotion-Focused Therapy.
This video is an excerpt taken from two training videos featuring Les, available to purchase at the following links:
www.cpcab.co.u...
www.cpcab.co.u...
This material includes an EFT therapy session, commentary about the session from Les Greenberg and 40 minutes of bonus content.