This trial is a single-center, randomised, double-blinded, two-treatment, two-period cross-over, 6-hour euglycaemic glucose clamp trial in subjects with Type 1 diabetes mellitus. Each subject will be randomly allocated to a single dose of BioChaperone insulin lispro 0.2 U/Kg and a single dose of Humalog® 0.2 U/Kg on 2 separate dosing visits.