Type 2 diabetes is a major risk factor for heart failure. Large-scale prospective studies and biobanks are an ideal resource to characterise high-risk populations and identify early markers of disease. Our goal is to quantify cardiac function in men and women with type 2 diabetes and no prior cardiovascular disease. We defined a cohort of type 2 diabetes in the UK Biobank using multiple ascertainment pathways including ICD codes, self-report, and circulating HbA1c. We then extracted ECG and cardiac magnetic resonance image-derived biomarkers related to diastolic function and cardiac autonomic neuropathy, and assessed these relative to reference ranges and current clinical guidelines. We identified 1781 subjects with type 2 diabetes; the cohort was mostly male, overweight, and elderly. We found that males and females with type 2 diabetes exhibit a QTc interval in the upper boundary of normal clinical ranges, with 272 subjects (15%) meeting age- and sex-specific clinical criteria for QTc prolongation, while 668 subjects (38%) had a ventricular rate above 70 bpm. These markers may indicate a higher risk of adverse cardiovascular complications. Left ventricular mass, end-diastolic volume, ejection fraction and wall thickness were found to be within normal ranges, suggesting an absence of perceptible structural remodelling.