Years ago I used to do trading systems and we provided private wire circuits for banks etc.
We had a guy going to install a router for a new circuit at Barclays in canary wharf. While mounting the router in the cab he (accidentally and didn’t realise) knocked a power cable out of this rather shitty old IBM server and within 10mins there were lots of people running around like headless chickens.
Turns out that old netfinity server was running the equities market trading platform for them.
I was on site for a meeting and went with them to the data centre where the engineer was being escorted out by two security guards. The Barclays IT bods were going batshit crazy until I asked some rather simple questions
Why is something so critical only using a single power supply?
Why was the power cable not secured in place with a retaining clip or why didn’t they use a locking IEC?
Over the years I’ve done lots of work for trading/banks etc and having seen their processes and data centres there’s certain banks I will not go near with my own money:
Barclays
Halifax
Lloyds
Tesco (post RBS)
AA
The vast majority of outages are changes that have gone wrong and it was shocking how badly Barclays ran their change processes, regression testing was an alien concept to them.