Theives make off with an estimated £25 million and what can really only be described as one very calculated and well executed plan (read: financed).
Check it out at Wikipedia:
http://en.wikipedia.org/wiki/Securitas_depot_robbery
Basically, they kidnapped the branch manager by impersonating police officers while simultaneously kidnapping his family, again by impersonating police officers. Then with the right amount of motivation applied (ie. do what we say or say goodbye to your family) about 6 people got in and tied up 15 guards then made off with £25 million in bank notes. Surely that would weigh more than a few tonnes…
UPDATE: Looks like teh revised estimate for the cash they made off with is now somewhere in the £25-50 million range…