Although you can apply direct via Linkedin, almost all employees are hired via recruitment agencies who pre-vet applicants. The only successful applicants I have meet while working here either came via recruitment agencies or were referred by people already employed by the Group. I think this is because these applicants have gained some insight into how the Group works.
Two stage interview process.
First stage:
Face to face interview with HR and hiring manager.
Second stage:
Face to face or phone interview with hiring managers boss.
No testing required in general, except for junior roles where an excel or word test might be required.