Why small-tube boilers and geared turbines belong together

Would Agincourt have adopted either 18-inch guns or small-tube boilers to avoid making too many changes at once?

The combination remains plausible: three twin turrets would be a layout change, while geared turbines would be the additional technology paired with small-tube boilers.

A proposed limit on simultaneous innovations raises the question of whether Agincourt could combine new guns with new machinery. Reducing the battery to six guns in three twin turrets would change the layout without necessarily introducing a new turret technology. Geared turbines would be the additional machinery development, since they would help exploit small-tube boilers fully. The appearance of these technologies in later ships supports the reconstruction, although it does not prove that Agincourt had a settled specification.