Accounts of building collapses at Venice and Beauvais help to demonstrate that structural failures can occur through changes in soil (perhaps in the level of the water table) or masonry (from mortar shrinkage or stone decay). Stabilisation works carried out on the tower at Ely by the author have involved removal of nineteenth century external straps, corner tie bars (possibly unnecessary) and grout forming a solid core encircling the inner wall surface and reinforced by rods inserted through the outer wall surface. The vibration and cracking of towers due to bell-ringing are potentially significant, as are the effects of wind; square solid towers intended as pinnacles can be overturned by the wind if they are too tall. The development of cracks in both solid walls and square hollow towers can be explored using simple equilibrium approaches to find the angles at which the walls and towers lean enough to first crack and later be overturned. Cracks appear in walls at smaller angles of leaning than in comparable thin-walled towers, but overturning occurs at rather greater angles for walls than for towers.