The magnetic susceptibility data can be simulated using exact diagonalisation 18 and an isotropic spin-Hamiltonian 𝐻 ̂= -2 ∑ 𝐽 𝑖𝑗 𝑖<𝑗 𝑠 ⃗ ̂𝑖 • 𝑠 ⃗ ̂𝑗 with a coupling scheme that assumes just one independent exchange interaction between nearest neighbours, J = + 4 cm -1 with g = 2.30 (Fig. , black curve). The addition of a next nearest neighbour interaction makes no difference to the quality of the simulation. Given that this interaction is computed to be very weak and ferromagnetic by DFT (vide infra) this is to be expected. The DFT calculated values for the seven crystallographically unique interactions also simulate the susceptibility well if they are scaled by a factor of 1.4 (Fig. , red curve). This simple isotropic model, however, does not explain the low temperature magnetisation data, which requires inclusion of the single ion anisotropy of the Ni ions, D(Ni), to be included 𝐻 ̂= 𝐷 ∑ (𝑠 ⃗ ̂𝑖 • 𝑒 ⃗ 𝑖 )