Looking at Google Earth shows the remains of the then Taxiway Alpha when it had to be moved south and then north before being put back along its present position for tunnel work.
This 1998 photo shows the southern taxiway position in use with the northern part started for completion at a later date before being moved back into the middle.
They must be planning night time closures for what must be 3 moves of the taxiway as the cut and cover Dart tunnel is put in.