  A new family of higher spin algebras that arises upon restricting matrix
extensions of $\mathfrak{shs}[\lambda]$ is found. We identify coset CFTs
realising these symmetry algebras, and thus propose new higher spin-CFT dual
pairs. These higher spin theories arise naturally as a subsector of string
theory on ${\rm AdS}_3\times {\rm S}^3 \times {\rm S}^3 \times {\rm S}^1$ for
specific ratios of the radii of the two spheres.
