Withdrawing 5,000 GBP is nothing and won't be an issue, if you have a pattern of doing so.
It's also less likely to raise alarms if it represents a small portion of the client's wealth.
Withdrawing 5,000 GBP out of nowhere raises questions. AFAIK, we don't know what happened prior to this video recording started. He might have said things that gave the bank genuine cause for concern.
The bank as a whole doesn't care about a 5,000 GBP withdrawal. It's not like there's a run on the banks that they are preventing by refusing this guy in this way. When banks prevent bank runs,︀ they usually just close the branches and refuse entry.
The bank cares about overzealous draconian︁ regulations, imposed in the name of prevention of money laundering. They can get hit with︂ fines that exceed the lifetime value of the account relationship for failing to do proper︃ checks and, if reasonable suspicion exists, refuse a specific service.
Blaming banks for all of︄ this is a little short sighted. The fault lies with regulators for creating this environment.︅ Banks don't want it.