Where HMS Belfast's forward guns are aimed

Where would HMS Belfast's A and B turrets hit if fired along their displayed alignment?

The London Gateway service area, described as twelve miles outside London.

The target identified for HMS Belfast's forward A and B turrets is the London Gateway service area, described as twelve miles outside London. The answer concerns the museum ship's displayed gun alignment. One participant recalls learning it during visits to Belfast, and another notes that the information is written inside one of the turrets.