This is the unfortunate result of a tree being too close to brickwork! Even if a tree appears not to be particularly close to a structure, it is important to remember that root systems can be just as large as the canopy of the tree. Heave (expansion) happens like this very easily with mature trees, even on seemingly solid structures such as concrete. You may have noticed this on the tree-lined streets of London, particularly those with mature London plane trees - they badly damage the pavements, causing them to rise and crack.
If you do have any trees near buildings or walls, make sure to keep a close eye on any cracks. Although small cracks in brickwork may occur over time, if it is caused by tree proximity, then the crack will be diagonal and wider than 3mm - you can test this by seeing if a 10p coin will fit in the crack. If it does, it is best to act as soon as possible, by beginning removal of the tree/s, or the brickwork may end up being destroyed, as it has in this case.
