The A380 has a wingspan of 80 metres. Because of this, due to wingtip clearance, it can't taxi along A or B on the northern side of LHR. Consequently, for a takeoff on 27R it must push back to face south from T5 and go around the southern taxiways until it gets to the eastern end of LHR, then head to 27R.

Taxing is probably the biggest challenge on the 380 at many airports.