St Helena's runway will be 1500m - its supposed to have relatively big 'shoulders' and taxiways etc.. (being a brown job i have no idea what that means...), but its still only 1500m.
from recall the view is that to be of any use regarding 'those islands', we'd need a runway at Tristan de Cunha, a further 1000+ miles south - and the topography just makes that a complete no-no: the only area on the islands almost flat enought to take a runway also happens to be the islands main farming area, and the island is a cliff, so actually getting stuff from ships to a contruction site is a nightmare...