Amazing Grace, a fine film about William Wilberforce's long campaign to abolish the slave trade (shown on STV last Friday), served as a reminder of this powerful sonnet on the subject by the Guyanese-born John Agard in his 2006 collection We Brits.

John Newton (1725-1807) was a slave-ship captain who realised the iniquity of the trade, became a Christian minister and composed many hymns, including that most poignant one, Amazing Grace.

NEWTON'S AMAZING GRACE

Grace is not a word for which I had much use.

And I skippered ships that did more than bruise

the face of the Atlantic. I carved my name

in human cargo without a thought of shame.

But the sea's big enough for a man to lose

his conscience, if not his puny neck.

In the sea's eye, who is this upstart speck

That calls himself a maker of history?

It took a storm to save the dumb wretch in me.

On a night the winds weighed heavy as my sins,

I spared a thought for those poor souls below deck.

Terror made rough waters my Damascus road.

Amazing grace began to lead me home.

Lord, let my soul's scum be measured by a hymn.