Every Sherlock episode RANKED

2. A Scandal in Belgravia

Lara Pulver's Irene Adler makes her Sherlock debut in this episode, which sees Sherlock attempting to retrieve compromising photos of a minor member of the royal family from her camera phone. She proves a real challenge for the usually cool, calm and collected detective and - after faking her death - convinces him to crack a code that will allow Moriarty to foil a British counter-terror operation.