"The Great Heist" refers to a significant robbery that took place in London in 2006, where a group of criminals stole £53 million from the Securitas cash depot. The heist involved meticulous planning, including the use of fake identities and inside information, allowing the thieves to bypass security measures. The operation was executed in broad daylight, with the gang holding employees hostage to gain access to the cash. Following an extensive investigation, several members of the gang were arrested, and a portion of the stolen money was recovered, but much of it remains missing.