Joslyn Seaton, aged 27, was pronounced dead in his cell at Leeds Prison on Saturday, January 25.
Police made several appeals to trace Seaton after he failed to comply with terms of his sentence.
The first appeal was made after Seaton, who was said to have links to Bolton, had served two years in prison.
When released last year he again failed to comply with licence conditions and was arrested again after a police wanted appeal.
Both of the robberies he was jailed for involved Seaton sitting behind a cab driver, pulling the seatbelt tightly around the drivers’ necks and demanding money before punching the drivers several times.
In the second attack, the driver was dragged from the taxi and punched and kicked.
He was jailed for a minimum of 21 months but was given an indeterminate sentence for public protection, meaning he was on a permanent licence.
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A prison service spokesman said: “HMP Leeds prisoner Joslyn Seaton was found unresponsive in his cell at 4.42pm on Saturday, January 25.
“Prison staff attempted CPR and paramedics attended but he was pronounced dead at 5.16pm.
“As with all deaths in custody, the Independent Prisons and Probation Ombudsman will conduct an investigation.”