Most airliners have bloody good brakes. I would guess there is at least one airliner a day whose goose is saved from running off the end of a runway by reverse thrust. St. Helena won't have ice or snow and maybe not much "wet" runway but the cliffs at each end are enough worry. An Avro RJ100 dribbled off the end of a 4600' runway in Norway only 10 years ago and broke apart, burned and killed 4 after falling down a 50' cliff. The auto spoilers failed to deploy and the runway was wetter than anticipated.