We investigate the dynamical behaviour of the Sherrington-Kirkpatrick mean field model of spin glasses by numerical simulation. All the timescales τ_x we have measured behave as ln (τ_x) ∝ N^ε, where N is the number of spins and ε≃1/3. This is true whether the autocorrelation function used to define τ_x is sensitive to the full reversal of the system or not.