I applied online. The process took 2 months. I interviewed at GCHQ (Bude, England) in Jan 2019
Interview
The process was very long winded but insightful. It took a long time to do the application and online tests. The interview was a half a day and it was a real treat to attend the Bude facility but looks like I did not quite fit what they were looking for.
Interview questions [1]
Question 1
How does the internet work? What is encryption etc