Fill in the right forms of the past perfect.

1. Nobody (hear) of Aberfan before
October 21, 1966, when a coal tip went down a mountain.
2. When the tip reached the school, it (destroy)
a farm cottage on its way.
3. At Pantglas Junior School, just below, the children
(return) to their classes after singing All Things Bright and Beautiful at their assembly.
4. The workers up the mountain (see) the tip
start going down but they could not raise the alarm because their telephone
(steal).