Sherlock trailers teased on BBC ahead of New Year's Day return

Sat in his leather arm chair with an expressionless gaze at the watery floor, Sherlock looks deep in thought over his latest case.

The new teaser image and trailer for the long-awaited fourth series has given fans plenty to speculate over, with 221 Baker Street littered with clues over what is to come.

A 15-second promo for the...