Campaigners fighting to save a children's heart surgery unit have been left disappointed after the Court of Appeal ruled that consultations which proposed its closure were lawful.
Bosses at the Royal Brompton in Chelsea now fear that, if the current plans are approved, the future of the entire hospital could be under threat.
But those involved in the planning say no final decision has yet been made.
Liz Wickham has sent this report.
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The meeting was arranged in the wake of Wednesday's terrorist murder of four people in Westminster.
Dozens of women gathered on Westminster Bridge to form a human chain in a show of solidarity with the victims of Wednesday's terror attack.
In a wide-ranging Peston on Sunday interview, he said Parliament security needs reviewing and the PM's counter-terror strategy is flawed.