The 40-year-old man who died in Worksop town centre has not yet been formally identified.
A post-mortem examination is due to take place to establish the cause of death.
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Specially-trained prison security teams were sent to HMP Hewell near Redditch, after trouble broke out on one of the prison's wings.
Scattered showers will develop through the late morning with some heavy, perhaps thundery downpours.
It will be a largely dry start to Sunday with some sunshine but showers to develop.