In Edwards v National Coal Board [1949] 1 All ER 743 CA, the Court of Appeal held that 'reasonably practicable' is a narrower term than 'physically possible' and implies a computation between quantum of risk on the one hand and the time, cost and trouble of safeguards on the other. If a defendant can show a gross disproportion between them, the risk being insignificant in relation to the sacrifice, the duty holder discharges the onus that is upon him or her.