To walk back from C Gates to B Gates or A Gates
Take the TTS lift down to level 2, at the end of the platform there's a door, with a button next to it to open the door, use this to get in to the TTS walkway.
Do you need to re-clear security for either of these options?
No, you do not reclear security, that's the whole point of avoiding a train arrival into T5A.
This option is no longer valid then?