They contact you on a platform called Hackajob and ask you to make an application. An employee of the Civil Service is even scheduling an interview with you but actually it is not really an interview, it is to incite you to apply and detail their application process. Previously I have been very disappointing with Home Office application jobs, so I stopped applying on their website as they definitively didn't like my profile. However I felt this time it would be different as I was personally contacted. Unfortunately I received a rejection email after about 2 weeks on a Sunday afternoon. I don't know what the hell they contacted me and wasted my time if they didn't like my profile. Maybe they need a minimum number of applications? Anyway if Home Office or any governmental organisation contact you to apply, just simply don't apply, it is a waste of time: they process is pretty long as you need to re-write your CV and a cover letter. Don't waste your time because it looks like they love wasting yours