Loz_S, Drawings are from Building Construction by W.B. McKay, Volume 1 (of 4), pub Longmans. The originals are long out of print but there are used copies about and Donhead have done a reprint of volumes 1 to 3 at £69. Mine, vols 1-3 and vol 4, by his son JK McKay, cost me 5 pounds and 17 shillings in 1967. Volume 1 was actually first published in 1938.
I think that, although limited to pre war (WWII) practice, volumes 1 to 3 cover the basics of building construction better than Mitchell’s, nicer drawings and clear text. On the other hand, Mitchell’s is far more comprehensive and relatively up to date.
If interested in old stuff, the other classics are the 3 volumes of Architectural Building Construction by Jaggard and Drury first published in the early 1920’s.
Ben, my description of the joint shown in the photo was incorrect. After posting I looked at another one in the workshop. What looks like a mitre of the moulds in the photo is actually rather cruder. The profile of the glazing bar moulding has been transferred to the moulding on the rail and the rail cut away to form a shallow housing for the end of the bar. Its just enough to look right when assembled. I guess they were paid by the piece and spent the minimum time possible. Although not as perfectly executed as we might hope these have stood the test of time and only broke down due to decay because the putty and paint were neglected in recent years.
Every other joint had two wedges, one either side. I was caught out but actually it would have made no difference if I had found and removed it as the tenon was set in its spread position and even when I cut the wedge out I couldn’t press the timber back to its original form. I think I would have had to steam it first. All repaired now and my error hidden 
