The 7 October rescue freed Carlos Marin Guarin, who also goes by the name of Gustavo Anibal Giraldo, but is better known by his alias of "Pablo" or "Pablito".
It took place as he was about to be moved from the prison in the region of Arauca, near the Venezuelan border, to the capital, Bogota.
Four ELN rebels entered the prison, led by a woman, who threw her boss a pistol. The rebels blasted their way out of the jail, killing one guard, wounding another and sending a further six scurrying for cover.
Waiting outside were two motorcycles and a van with more heavily armed rebels giving covering fire. "Pablo" jumped on the back of a motorcycle and was believed to be in Venezuela less than an hour later.
Pablo was the highest-ranking ELN rebel to have been captured in the five decades the guerrillas have been trying to overthrow the government. So his escape was an embarrassment for the government, leading President Alvaro Uribe to suggest there had been inside help.
"We gain nothing from increased security if there is corruption in that security," said Mr Uribe, a day after the break-out.
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