Little is actually known about Pan Nam, who passed away in 1996.  He comes from the Da Fa Min Kam (Painted Face Kam) and Chan Wah Shun (Yip Man's Sifu) lineages.  He was said to be a Hung Kuen practitioner for a long time before learning Wing Chun.
About Pan Nam's Wing Chun:
"The Shaolin Temple monk, Yi Chum, was said by Pan Nam to be the true founder of Wing Chun. Yi Chum taught Tan Sau Ng, who taught Dai Fa Min Kam, Wong Wah Bo and Leung Yee Tei (Leung Jan's teachers) and so on until Pan Nam (see lineage chart below).
This branch of the Wing Chun family tree has not only preserved a different, possibly older, form of Wing Chun but also the Qigong (Chi-Kung) exercises that Master Pan said have been a part of the Wing Chun System from its inception.
The techniques in Pan Nam Wing Chun are relaxed until the moment of initiating the attack. The stance uses a 50/50 weight distribution. The toes are pointed straight forward and advances are made with stepping movements as opposed to dragging the rear leg. The system emphasizes triangular footwork, as compared to linear directions. The punches can be directed towards any line from the shoulder. The emphasis is upon a sudden move that controls the opponent, disrupts the opponent's stance, and forceful strikes to vital points.  In Chi-Sao, the hands do not roll; they are in contact with each other a bit similar to the way the Tai Chi Push-Hands exercise is performed. 
Rather than thinking of one's own centerline, the re-direction of the opponent's centerline is the key to successful attack. At that point, one's attack can occur from any direction of one's shoulder. Logically and physically, there are many advantages through striking from any angle (as opposed to the centerline only). The idea of intercept prevents the opponent from placing one in a position of defeat - trapping, pinning, stance disruption, etc. The principle of intercept is to redirect the opponent's movements before the opponent can complete a move, offensively or defensively.

This redirection of the opponent's energy is conducted through (1) sensitivity, (2) "going with the flow" of the opponent's movement (as distinguished from "giving in"), and (3) proper contact with the opponent's arm or leg. Without the concept of intercept, one is reliant upon either eye-and-hand coordination (which may be deficient to superior reach or speed) or simply a contest of brute force (which may be deficient to superior strength)..." 

Quoted From

Reprinted with permission from THE WING CHUN ARCHIVE.