Are you sure it was Dutch Roll you witnessed and not a demonstration of the handling qualities ?
I ask because in the book I mentioned above is the following comment.
".....while instantaneous recovery could be made from any tendency to Dutch roll"
Roland Beamont said it was most enjoyable to fly and was surprised how little there was to do once in the cockpit.
He also stated that it was ''a pleasant responsive aircraft with adequate longitudinal and directional characteristics in the range of flight conditions checked".
He found the adverse yaw was no more obtrusive than on the P1.