The golden hour is that last hour of the day when the setting sun casts the world in its warm yellow glow, draws eyes westward and camera phones from pockets. Then, like the flick of a switch, that warm glow turns to a grey-blue coolness as the sun disappears below the horizon.

But just a little while into twilight something quite unexpected happens – at least it was unexpected for me the first time I noticed a strange warm light envelop everything.

Initially I was puzzled where this warm glow was coming from. Then its source became apparent in the western sky. That hint of green-orange – however dim – on the horizon was so much brighter than the approaching night and brought a gentle afterglow to the world in the fading light.