In interview, your chances of success hinge not just on your ability to do the job – but on your ability to demonstrate your ability to do the job.
The artificiality of the interview environment irks many people. “Why can’t they just let me do the job for a week, and I’ll prove myself,” is one reaction. But that’s not how things are done: and so you must prepare yourself to be convincing in interview.
Knowing how to do the job is only one half of the equation – it’s how you communicate that in that room that really matters.
People with specialist experience often rail against this, but there is no real alternative. If you don’t convince the employer, it’s unlikely anyone else will do so on your behalf.