Meredith Kercher's sister Stephanie has said there are "more stages" to come before they feel they have learnt the truth about the British student's death in Perugia in 2007.
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The former foreign minister said that Parliament should be willing to reject a deal that is not in the UK's best interests.
The country's top defence officer said the force may ignore any order to launch a nuclear attack which is deemed to be illegal.
Navy officials say they have received seven short satellite calls which are though to have come from the submarine.