Vicky Pryce, 60, emerged from East Sutton Park Prison near Maidstone, Kent, via a back exit.
The mother-of-five was driven away with her lawyer Robert Brown, pursued by press photographers who been camped outside the Category D open jail for women and young offenders.
The ex-wife of former Cabinet minister Chris Huhne's has served around a quarter of an eight-month sentence for taking speeding points for him.
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A 23-year-old man has been arrested in connection with the attack at Manchester Arena last night.
Theresa May says police think they know identity of lone bomber as she contrasts "warped" terrorist with courageous emergency services.
Donald Trump has branded those who take part in terrorist acts as "evil losers" in the wake of a suicide attack at Manchester Arena.