T2K is a long baseline neutrino oscillation experiment designed to measure the θ23 and θ13 mixing angles to high precision using νμ disappearance and νe appearance respectively. A major component of the T2K near detector is the electromagnetic calorimeter; the construction, commissioning and operation of the ECal is describe in detail in this thesis. T2K uses the dominant CCQE neutrino interaction as a clean and simple signal in oscillation measurements. However, other interaction processes interfere with the oscillation measurements, a large contribution to this interference for νμ analyses is from CC1π+ interactions. This thesis measures the νμ CC1π+/CCQE cross-section ratio on C8H8 using the T2K near detector. As an internal consistency check, the flux integrated ratio is calculated as RMC = 0.235 ± 0.019Stat ± 0.047Syst for MC and RData = 0.237. The ratio is also measured as a function of incident neutrino energy and finds an agreement with NEUTMC of χ2/NDOF = 6.6/6.