A Senior House Officer is a curious beast: After one year as a doctor in the National Health Service
and finally fully registered with the GMC
he/she finally arrives in the specialty he/she is interested in, and is left in charge of a couple of JHO's
and a whole hospital at night.
Now working unsupervised for most of the time, there's only a registrar and (sometimes) a consultant to ask for help. This sorry state of affairs will continue for a couple of years until he/she finally passes her postgraduate exams (membership) and the doctor finally gets a job as a registrar.
The SHO is considered to work even harder than a JHO and bears the brunt of the responsibility of what happens during a normal workday on a ward and at night. Most likely to be only 22 or 23, this is a lot to bear for somebody in his or hers first couple of years of their working life.