With the weather man already warning of the wettest winter in years it is essential that any cracks in brick walls and lintels and any damage to balconies is repaired using the correct products and techniques. Failure to make timely repairs could result in the damage becoming far worse and far more expensive to repair.
The chance of the crack in your wall being caused by subsidence and requiring underpinning and/or rebuild is very slim.
Cracks in walls are the result of some kind of movement causes stress that the bricks cannot sustain. Movement can be caused by a variation in moisture, either in the wall itself or in the ground that supports it, temperature variations, chemical reactions or by replacing load bearing, wooden windows with non-load bearing UPVC windows. Some movement comes and goes with the seasons and other movement is permanent.