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That, of course, isn't the whole story. At some point your perp has to leave the room with a view and go to the gate of 5A During that journey they can't see what's happening. For all they know a member of the T9 left the Tapas as they left their view, reached 5A before them and is now inside.
No not necessarily. If 2 working together 1 could remain in the apartment and use a light/torch as a signal to the actual abductor eg two light flashes = T9 about to start their starters, possibly using binoculars. If solo he/she may well have hid inside apartment, garden or alley waiting for a McCann check to be over knowing he/she would have 30 mins.
JT/ROB/FO/MO were carrying out their checks via the front. The perp only needed a clear second or two from the alley to the side gate. Is it possible the perp climbed over the wall from the alley into the back garden? I'm assuming the garden then leads up to the balcony?