Designed by Harold Dennis Taylor. The Cooke triplet proved to be an influential design, it was made in several series by Taylor, Taylor & Hobson and was widely copied by other manufacturers. The original patent shows a lens consisting of two plano-convex elements each side of and equidistant from a bi-concave element.

The series V was intended for architectural, copying and reproduction work.

The Portrait Anastigmat produced variable softness (spherical aberration) by altering the separation between the lenses. The finger grip to rotate the lens barrel was introduced in the early 1920s, the lens was advertised into the 1950s.

The series VI lenses had an aperture of f5.6, the lens had pulleys attached to it allowing the photographer to alter the degree of softness when behind the camera. The series IIa had an aperture f3.5. The IIc series were portrait lenses but without the variable soft focus feature.

The III series was for general purpose work, the 11" model covered a whole-plate at full aperture.

The Aviar was developed during World War I for photo-reconnaissance work, after the war its use was extended to general photography. Comprises four separate glasses.