How do you become part of MI5?

The Security Service (MI5) recruits from many sources, and by many methods:

1.) Adverts in national and other newspapers;

2.) its website;

3.) "Talent spotters" in universities and elsewhere (eg companies, law firms etc) may "sound out" potential applicants via discreet approaches - might they be interested? etc

4.) ...some may enter MI5 via the Police or Armed Forces, especially if they have particular skills.

All of the above are, however, just preliminaries - potential recruits will then be screened/ selected very thoroughly (interviews; aptitude tests; psychometric tests; medical exams; "positive vetting" - ie high level security checks etc), and most will probably be rejected. Only a few (probably less than 10%) of those expressing an interest in joining MI5 will actually be accepted for training.