Kevin McCloud ascends the tallest council block in Europe, Trellick Tower in London's Notting Hill. He chronicles the 322ft structure's fortunes, from architect Erno Goldfinger 's original sixties vision of "streets in the sky", through its rock-bottom reputation in the eighties as a vertical slum plagued by drug abuse and crime, to its current English Heritage Grade II Listed status. With the help of long-term occupants and members of the residents' association, he discovers what has caused these radical changes.

• Kevin McCloud