Bold robbery

You are the most elusive and dangerous criminals in the world. You have hundreds of robberies to your credit and not a single failure. Now, you, disguised, are driving from another robbery, nothing presages trouble, when suddenly your car breaks down near a nondescript private bank. On your radio at a secret wave, you hear the voice of an unknown man who reports that you have exactly one hour to get a special diamond for him from this bank. Everything else you can take for yourself. Otherwise, the police are already on standby and are waiting for the address of your location. You have no choice, you need to rob now. There are many questions. Perhaps along the way, you will manage to find the answers to them. Who is this man on the other end of the radio? What is this diamond and why does the stranger only need it? And how did he find you.