Despite being stabbed five times by the London Bridge attacker, one of Friday's heroes fought with the terrorist "until the end" as he bought time for others to escape.
Sky News has been told of the extraordinary account of Lukasz who was working in the basement at Fishmongers' Hall when Usman Khan launched his deadly attack.
However, the death toll could have been higher but for the actions of a number of bystanders.
Describing the shocking incident, Fishmongers' Hall chief executive Toby Williamson hailed his colleague's actions.
"You're not going to see Lukasz. Firstly he's too modest and secondly there's no camera footage," he said.
"He's washing up glasses in the basement. He hears the screams. He's first aid trained so he makes the conscious decision to go upstairs. It's pretty obvious what's happening.
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"The terrorist is brandishing two knives with victims all around screaming and people cornered.
"He pulls off the wall this narwhal tusk and takes the fight on. In the next minute he's on his own.
"He's buying time for others to escape. In that time he makes a stab towards the terrorist and knows something is wrong as he hits him in the chest and it bounces off.
"He's got a vest on of some sort. At that point there's a vicious knife fight in which Lukasz takes five cuts all the way up his arm. He's hurt badly but doesn't flinch for a minute.
"He's then joined by two or three others, and now overwhelmed by numbers the assailant goes down the stairs."
After another fight in the building's foyer, Khan, 28, breaks through the doors on to the steps outside.