Compartmental models are increasingly being used to quantify diffusion MRI signals from tumours. We have developed a complex, multiscale mathematical modelling platform for simulating tumour pathophysiology, using high-resolution optical imaging data from complete tumour samples. Diffusion MRI signals from these tumours were simulated, including vascular flow and intra- and extracellular diffusion. These data were fitted to the VERDICT compartmental model, and the resulting parameters compared against ground truth simulation values. Cell radius and intra/extracellular fractional volume parameters and respective ground truth values were strongly correlated. A more complex relationship was found in vascular volume fractions.