I applied online. The process took 6 months. I interviewed at BAE Systems (Rochester, South East England, England)
Interview
Standard online assessments with personality and numeracy tests, then phone interview with general questions like why do you want to work here and past experience then live interview. Large period of time between phone interview and final stage
Interview questions [1]
Question 1
Name a time you made a mistake and how you overcame it
Online Assessment, then Phone Call, then In person Interview.
All were relatively simple. As it is an Intern role, they expect baseline understanding rather than expert knowledge, as you will learn.
Multi-round interview process with first interview being HireVue and the final interview being an online interview with two staff members (during Covid).
Make sure to know why you want to work a particular role (i.e. systems engineering) and not just generic answers about BAE as a whole.