Beware the Chairman of the Bank
It's the early-mid 1990's we are an outsource supplier to a very large UK bank stock brokering operation - They have invested heavily in a clustered VAX infrastructure that has eliminated most of the single points of failure, except one big one in that the cluster (And shadowed disks) were in the same physical data centre and in fact in the same large bank customer only data center hall/room.
This clustered VAX infrastructure worked extremely well and the bank was very happy with the high availability, much improved speed and the service we were delivering, so much so, they wanted to bring a bunch of their senior executives to our facility to show them what the banks money had been spent on.
Cue to day of the visit, everything was going really well, the final part was an escorted visit to the actual data room where all their kit was housed - Some questions asked by executives but suddenly the chairman announced that he understood that it was impossible to shutdown the computers (Great selling of high availability by the account manager) and suddenly the chairman reached out to the big red button on the wall. Literally mill-seconds from disaster I managed to intercept the chairman's had (with quite a bit of force) and stop him hitting the EPO.
However the aftermath was me apologising for the "assault", the bank chairman thinking we had something to hide and overall 12 months to rebuild the customer confidence in us - Even though we did stop a complete powerdown which would have cost them hundreds of thousands.
Lesson learnt, never ever take customers into the data center even if they own it - So next step was a couple of windows installed so customers could see but not touch.