‘The principal periods in the history of the monument were firmly fixed and the complicated relationship between its component parts was securely defined’. With these words Sir Ian Richmond in 1950 reviewed more than a decade's work on Hadrian's Wall. Ten years before he had written: ‘As the great scheme proceeded, modifications were introduced, some structural, of interest only in defining the order of progress, others amounting to a thorough revision of the design. The most important of the latter was the construction of forts on the Wall itself. His analysis of ‘the fort - decision’ remains unchallenged, but in his 1950 paper Richmond reported on details of the structure of the Wall: in particular those observed during the consolidation of Turret 26b and the relationship between the Narrow and Broad Walls. In conclusion he wrote: ‘Plainly these are minor puzzles beyond immediate solution here, important for those who would follow centuriae at work, yet not obscuring a vision of the main intention’.