We study a plasmonic metasurface that supports pseudospin dependent edge states confined at a subwavelength scale, considering full electrodynamic interactions including retardation and radiative effects. The spatial symmetry of the lattice of plasmonic nanoparticles gives rise to edge states with properties reminiscent of the quantum spin Hall effect in topological insulators. However, unlike the spin-momentum locking characteristic of topological insulators, these modes are not purely unidirectional and their propagation properties can be understood by analysing the spin angular momentum of the electromagnetic field, which is inhomogenous in the plane of the lattice. The local 1 sign of the spin angular momentum determines the propagation direction of the mode under a near-field excitation source. We also study the optical response under far-field excitation and discuss in detail the effects of radiation and retardation. dospin Topological insulators are materials which are insulating in the bulk but which have conduction surface states protected against disorder (1). The remarkable properties of these states in electronic systems has inspired the search for photonic topological insulators (PTIs), which aim to guide and manipulate photons with the same level of control and efficiency (2-6). Systems which possess these effects whilst preserving time reversal symmetry are appealing as they do not require complicated experimental setups such as strong magnetic fields or bianisotropic coupling. Motivated by this, a proposal to emulate the quantum spin Hall (QSH) effect in photonic crystals was presented by Wu and Hu in Ref. 7. Effects reminiscent of the QSH phase such as a band inversion between dipolar and quadrupolarmodes, and pseudospin dependent edge states are realised but, rather than relying on the time reversal symmetric pairs characteristic of electronic systems, they instead rely on the spatial symmetry of the lattice structure. As a result, the edge states have a reduction in backscattering over trivial ones (8,9). The method has since been applied to a variety of bosonic systems (10-14), and has recently experimentally been demonstrated in the visible regime (15).The combination of topological effects with plasmonics offers the possibility of precisely controlling light on the the nanoscale. The strong enhancement and localisation of electric fields due to localised surface plasmon (LSP) resonances (16) is a widely employed platform for light confinement on the nanoscale (17,18). Plasmonic metasurfaces can be formed by arranging plasmonic nanoparticles in two-dimensional (2D) lattices, where the LSPs become