Fault on Train

So, yesterday on the Jubilee Line (and some of us still want to call it the Fleet Line, I'm afraid), at London Bridge the message came over the speakers: "I'm sorry there is a fault on the train, we have to take it out of service.  Everybody off, please".  OK, not a big problem, those trains are pretty frequent.

But on the platform came "Sorry, there is a fault in the CCTV".

What?  Is the CCTV so crucial now?  At first we thought it was an anti-terrorism rule, then that there was an insurance (passenger protection) issue.

But no explanation of why the CCTV is so crucial on the Jubilee Line. 

Does anyone out there know?