The first time I became aware of new stock being held at a dealers other than orders was in July 2009.
I called in at Williams on their old Bristol site and Henry had a brand new Plus 4 and a 4/4 Sport in the showroom, the later of which I drove and bought.
They were both Sport Green with Tan leather I just assumed he had ordered on spec as it was the Centenary year and demand would be high but with hindsight this could have been the beginning.