A Manchester City youth player will return to prison after mistakenly being released on Monday four months into a 16 month sentence for killing a brother and sister while speeding in his Mercedes in central Manchester.
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Britain's Prison Service said it would hold an investigation after 18-year-old Courtney Meppen- Walter was released in error.
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"Police have been informed after a prisoner was released in error on Monday 1 July to ensure he is promptly returned to custody," said a spokesman.
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"Releases in error are very rare and we take any incident extremely seriously.
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"An investigation will take place into the circumstances that led to this release."
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Meppen-Walter was driving at nearly double the speed limit of 30 miles (48 kilometres) per hour when he hit a car carrying Kulwant Singh, 32, and his 37-year-old sister, Ravel Kaur.
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Both siblings, who hailed from the Manchester area, were killed, while Kaur's two sons, aged 16 and 17, were injured.
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Their relatives said they felt "let down" by Monday's mistake.
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Meppen-Walter, who was also the captain of England's under-18 side, is due to serve half his sentence in custody but may be released earlier and obliged to wear an electronic tag.
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The judge also banned him from driving for three years and ordered the sale of the car, with the proceeds to go to the injured passengers.