After the disappointing failure of the Valkyrie to gain orders, it was evident that Saunders' traditional wooden hulled flying boats were out of date.

This hull construction was used on all the Saunders and Saunders-Roe flying boats designed up to about 1935: the A.7, Cutty Sark, Cloud, Windhover and London.

Knowler's design replaced the internal stringers with external corrugations in the hull plating which needed no riveting and avoided the stringer-frame intersection.

The hydrodynamic novelty was less subtle: most flying boats had used hulls which in cross section curved outwards from the keel rather than take a simple V-form, chiefly to reduce "dirty" upward spray.

Certainly the Southampton had the more graceful lines, the rounded fuselage rising smoothly to the tail in contrast with the A.14's slab sided, linearly graded form.

By July, after almost flying 50 hours new structure was showing signs of weakness with slight distortions visible on the bottom just forward of the main step.