What saws were traditionally used for timber framing cuts in British practice? British-style backsaws don't seem to have cut depths any more than about 4", so how did they cut long tenons?
In the British tradition, such work would be done with a wooden bow saw (also called a buck saw). A nice feature of such a saw is the direction of the cut is nearly independent of where the handle is oriented, so you can cut a deep tenon as deep as you like, assuming the saw's frame is free to move. Such saws are in Europe in place of backed saw.