The vanishing  There are certain rules in the missing persons
game. Don't be a boy, don't be working class, don't be black. As
for persistent runaways, children in care or teenagers with
drugs problems, forget it... In the lead-up to Christmas, a key
period for disappearances, Martin Bright meets the families left
behind  In March this year, around the time Surrey teenager
Milly Dowler went missing, the body of a 14-year-old girl was
found in a disused cement works in Northfleet, a bleak Thames
Estuary town opposite Tilbury docks. The badly decomposed body
had been wrapped in tarpaulin by her murderer and left in this
desolate corner of industrial Kent, where they had good reason
to believe it would never be found.  On 27 March, four days
after Sally and Robert Dowler had made an emotional TV appeal
for the return of their daughter, the body was identified as
that of Hannah Williams, a schoolgirl from Dartford in southeast
London, who had gone missing almost a year earlier. On 21 April
2001 she had told her m