"A third of the mansions on the most expensive stretch of London's 'Billionaires Row' are standing empty, including several huge houses that have fallen into ruin after standing almost completely vacant for a quarter of a century"

The Guardian:

Exclusive access to now derelict properties has revealed that their condition is so poor in some cases that water streams down ballroom walls, ferns grow out of floors strewn with rubble from collapsed ceilings, and pigeon and owl skeletons lie scattered across rotting carpets.