We consider a simple travelling front model for the growth of glioblastoma brain tumours. Resection of the diffuse tumour cannot fully eliminate all cancer cells and therefore the tumour typically reappears. Nevertheless it is expected that resection may delay the overall invasion of cancer cells into the healthy tissue. We use a general reaction-diffusion model of front propagation and investigate how the delay of the invasion front relative to the untreated tumour depends on the accuracy of resection, proliferation dynamics and diffusivity of the cancer cells.