Emergency Lighting - different local circuits

[South Spark]

When installing non-maintained emergency lights where there is more than one 'local' lighting circuit e.g a three storey house is it best practice to have the Emergency Lights all on one lighting circuit and therefore testable with one key-switch or split between the lighting circuits with a key switch on each floor?

 

[Sintra]

Do them on the local lighting circuits. You can still use one key switch by simply running the emergency lighting supplies through a N/C contactor.