Nitrogen vacancy (NV) centres have emerged as an important system exhibiting promising properties for applications in quantum technologies, including quantum information processing, quantum metrology, and single photon sources. In our work, the dynamics of nitrogen vacancy colour centres in diamond are investigated at the single photon level. The system is pumped with a 532 nm quantum light and fluorescence is observed. The fluorescence signal registered by a single photon detector is compared with heralding photon reference signal and fluorescence decay is collected. This paves the way for development of novel quantum metrology techniques.