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.