Parents of Alfie and Harry McQuillan describe what happened when they discovered the overdose of morphine had been given.
One twin was given ten times the recommended dose while the other twin was given 17 times the normal dose.
Both died soon after the drug was given.
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The driver was not injured in the crash.
A new emergency department at the Leicester Royal Infirmary has opened this morning.
Footage of the police raid shows that the house had been entirely gutted and replaced with growing equipment.