A fast frequency support control scheme for voltage source converter based high-voltage direct-current (HVDC) links has been designed, simulated and experimentally implemented and validated. The effectiveness of the proposed scheme has been tested on simplified GB power system models with both averaged and switched converter models. System performance has been initially assessed using different software simulation platforms (PSCAD and MATLAB/Simulink). System validation has been carried out using an experimental test-rig. It is shown that simulation and experimental results agree on well when the fast frequency support provision is enabled. For completeness, the effectiveness of the control scheme has been tested for two contingency scenarios: (i) when a high-voltage alternating-current interlink in parallel with the HVDC link is disconnected, and (ii) for a substantial increase in system load.