Inflammation is known to be a powerful promotor of tumour growth that is difficult to measure and quantify in vivo. Here I propose a mathematical model to explore the influence of inflammation on tumour growth, and to determine potential consequences it may have on treatment and metastasis. We use various experimental datasets to parameterize our differential-equations-based model of cancer-immune interactions, focusing on the tumour-promotion caused by inflammation. Numerical simulations are used to explore potential mechanisms underlying tumour growth observations. Importantly, the model predicts that unbalanced inflammatory actions, and in particular, a pre-inflamed site, can cause growth disparities observed in experimental data. The model is then used to explore potential consequences of inflammation on metastasis post-surgery, when inflammatory conditions are altered.