At the time Arthur Koestler wrote his Reflections on Hanging (1956), Britain was still defying the trend among other Western democracies by continuing to apply the death penalty. Despite the country's celebrated liberal traditions, the UK clung to the practice of hanging people by the neck till dead, long after most of its peer nations on the continent had abandoned capital punishment as a brutal and archaic relic.
Today, that same mantle has passed to the United States. Great Britain has long since joined the rest of the democratic world by ending the practice of judicial murder. And so now, it is the U.S. that is the outlier; the U.S. that lags far behind the rest of its democratic peers in terms of moral progress by still executing a score or so of people every year, across its fifty states.