In the limited time available general principles won’t emerge if the content is dull. There won’t be an enthusiastic search for rules powerful enough to apply to a wider class of problems containing both dull and stimulating issues.

Yet given considerable variety in the mathematical world and Mr Wigley’s caution over learning a language, the search for higher order principles may not often be successful.

Since the examples of stones and rods could fall anywhere on an abstract continuum from dull to interesting, we should consider a worst-case scenario.

Suppose pupils start some key stage with very few interesting ideas. Is the national curriculum explicit about what to do next, or is it a dark alleyway crowded with carefully selected specialist topics lacking any user-friendly strategy to enlighten their delivery?

NEIL RICHARDSON 4 Sandal Avenue Wakefield.