One of many English large scale frame builders who over time bought out their rivals and eventually grew too big for their own good.  Examples from their early years through the 60's are said to be of extraordinarily quality.  However through the 70's and certainly in the 80's the frames became mass produced product.  However even these later examples are reported to be fine riding frame, just do not have the workmanship of the earlier frames.  Holdsworth bought out builders Claud Butler and Freddie Grubb among others.