Implacable carrier tonnage source problem

How reliable are H. T. Lenton's figures for Implacable and Indefatigable tonnage?

Lenton is a serious source, but the underlying primary sources vary; the 27,000-ton design context and plausible builder variation matter more than one exact published figure.

The Implacable-class figures show how naval historians work with conflicting primary-source values rather than a single clean number. Sister ships built to the same design can vary because builders use different steel thicknesses and construction practices, but that variation should remain within a plausible range. The Second London Naval Treaty removed the aggregate carrier-tonnage ceiling while retaining a 27,000-ton limit for each carrier, making a full-size design attractive. One explanation is that the Royal Navy described Implacable as a continuation of the Illustrious design study while selecting the larger study that better matched its requirements. The same family of studies also led toward HMS Unicorn and later light fleet carriers, placing the tonnage dispute within a longer design lineage.