This paper presents a comparison of the plastic collapse loads from experimental in-plane bending tests on three 90 degree single un-reinforced mitred pipe bends, with the results from various 3D solid finite element models. The bending load applied reduced the bend angle and in turn, the resulting cross-sectional ovalisation led to a recognised weakening mechanism, which is only observable by testing or by including large displacement effects in the plastic finite element solution. A small displacement limit solution with an elastic-perfectly-plastic material model overestimated the collapse load by 40%. The plastic collapse finite element solution produced excellent agreement with experiment