The recent development of electronic logbooks with secure off-device data storage provides a rich resource for research. We present the largest analysis of anaesthetic logbooks to date, with data from 494,235 cases logged by 964 anaesthetists over a 4-year period. Our analysis describes and compares the annual case-load and supervision levels of different grades of anaesthetists across the UK and Republic of Ireland. We calculated the number of cases undertaken per year by grade (median (IQR [range]) core trainees = 388 (252-512 [52-1204]); specialist trainees = 344 (228-480 [52-1144]); and consultants = 328 (204-500 [52-1316]). Overall, the proportion of cases undertaken with direct consultant supervision was 56.7% and 41.6% for core trainees and specialist trainees, respectively. The proportion of supervised cases reduced out-of-hours, for both core trainees (day 93.5%, evening 86.3%, night 78.6%) and specialist trainees (day 81.0%, evening 67.7%, night 56.4%).