How much access is needed to this connection box?

[StephenStephen]

We're having a section of external wall, currently plywood I think, rebuilt with block, cavity and brick.

The phone connector (see pic) will end up in the cavity, so we're thinking we need to build an access box into the inner (block) wall in case any work is ever needed on this connector.
How much access (ie; how big does the box need to be) could be required in the future? (open heart or keyhole surgery?!)

 

[Murdochcat]

If you still are connected to the BT copper network DO NOT put that in the cavity

 

[StephenStephen]

If you still are connected to the BT copper network DO NOT put that in the cavity

It is where it is. We're not moving it. What access is needed?

 

[sparkymarka]

None …because sooner or later it will be a fibre optic cable …