As an initial step, we compare the performance of the combined WTMetaD-IB AL strategy against downhill AL, using the reaction between the fluoride ion and chloromethane (R1) as a model system. The MLPs were trained at the CPCM(water)-PBE0-D3BJ/def2-SVP level of theory. While this study uses a relatively simple hybrid functional to compute the reference data, the same procedure could be applied with more accurate electronic structure methods. For WTMetaD-IB, the difference between two distances, C-Cl and C-F (r Cl -r F ) was used as CV, while for downhill dynamics a TS, optimised at the ground-truth level of theory, was used to generate initial training data. Fig. shows the gradual exploration of the PES for this reaction, with the training configurations depicted as black dots. Downhill AL starts from a series of structures generated by random displacement of the DFT-optimized TS, (AL iteration 0). These structures are located in the high-energy region of the PES (inner plot). In contrast, WTMetaD-IB AL begins with distorted (not optimized) RS configurations, as evidenced by the extended C-F bond and energies comparable to TS configurations (see Fig. and Fig. ).