David continues:

The first job was to create as accurate a plan of the building as possible. In doing this it soon became obvious that more photographs would be required, and it was necessary to obtain accurate dimensions for the bricks used, and if possible an accurate sizing of one of the bays for comparative purposes.

Fortunately through the auspices of the N gauge Society Roger was able to contact a colleague who carried out a survey and took more photographs.
From these an approximate plan was drawn, from which it emerged that the building was about 330 feet in length which translates as 660mm in N gauge. There were 9 distinct blocks or sections of the building and these were labelled A-I to assist in identification as the various parts of the model were drawn and cut out. A final and accurate plan would not be possible until all the detailed elevations were created (see fig.2).

Figure 2