A pensioner and her 25-year-old son have been released on bail after they were arrested on suspicion of encouraging or assisting a suicide.
A Sussex Police spokesman said: "It is an offence to encourage or assist suicide under the Coroners and Justice Act 2009 and officers are investigating whether any crime has been committed or is likely to be committed if they do not take action."
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There was something very striking about the pact, which implies the new agreement could remain in place even if the prime minister does not.