Tangent to our goal of developing accurate MLPs for DA reactions, we found that GAP regularisation could be harnessed to reduce the computational cost of developing CCSD(T)-quality potentials (SI §S4). For simple molecules, MP2 forces are accurate to within 1.1 kcal mol -1 Å -1 (0.05 eV Å -1 ) of their CCSD(T) counterparts (Fig. ), thus within the 'expected error' of the GAP. This removes the requirement for numerical CCSD(T) gradients. This strategy, combined with CUR selection, afford a 100-fold reduction in the number of required CCSD(T) energy calculations, thus greatly reducing the time required to train a CCSD(T)-quality potential (Table ). Furthermore, re-evaluating energies and forces from AL configurations with a different reference method (i.e. 'uplifting') reduces the computational cost associated with training WF-quality MLPs. Such strategies were also applied to other electronic structure methods. For example, uplifting PBE0/DZ configurations to MP2/TZ affords an ACE MLP within ± 1 kcal mol -1 of MP2-MD-sampled configurations (Fig. , DZ=double-ζ basis set, TZ=triple-ζ). These strategies enable us to attain a higher level of accuracy in the MLP at a reduced computational cost.