A modern loop-in ceiling rose will have three terminal blocks to accommodate the two cut ends of the circuit cable plus the switch cable. The red (live) conductors of the circuit feed cable run to the central live terminal block and the neutral (black) conductors run to the neutral block on one side, while all the earth conductors run to a common earth terminal. The red (live) conductor of the switch cable is connected to the remaining live terminal in the central block. Power runs through this conductor to the switch and back to the ceiling rose through the black (neutral) conductor on the switch cable. This 'switch-and-return' wire is in fact live when the light is switched on, and should therefore be clearly labelled by having a piece of red insulating tape wrapped around it to distinguish it from the other black conductors (which are neutral).
The black 'switch-and-return' conductor is connected to the third terminal block in the rose. The earth conductor from the switch cable is attached to the earth terminal that is shared by all the other earth conductors, including the one belonging to the actual pendant light flex if it is a three-core flex. The brown (live) conductor from the light pendant is attached to the terminal on the switch block while the blue (neutral) conductor from the light pendant is attached to the neutral block. You can identify the last ceiling rose on a loop-in system by the fact that, because the circuit feed cable does not have to exit out of the rose to carry on to the next rose on a circuit, only one set of cable conductors is connected, with the switch cable and lamp flex attached.
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