In Alnwick, Northumberland: A Study in Town-Plan Analysis (1960) M. R. G. Conzen split the town plan into three form complexes - the street system, the plot pattern and the building fabric - and showed that they change at very different speeds. The plot, not the building or the block, is the persistent unit: burgage plots laid out in the twelfth century still govern frontages long after every building on them has been replaced. He described the burgage cycle of progressive backland infill followed by clearance, and the fringe belt left behind wherever a town's growth paused. The method gave morphology a working vocabulary - morphological frame, plot series, plan unit - that can be read straight off cadastral maps.
It established the plot as the elementary and most durable unit of urban form, which is why plot size and ownership pattern predict what a street will look like better than any design intention does. Conzenian analysis underpins later work on fine-grain regeneration, typological design codes and morphological resilience from Britain to Italy and China.
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