Magical tunnel moments

Years ago, around the middle of January, we entered Wast Hills tunnel going north and everything was normal until we looked back. The ripples left by the boat were illuminated by the afternoon sun, which we could not see, and remained so until we'd almost reached the Kings Norton end. It looked like molten gold, lighting up the whole length of the tunnel behind us.

We'd always hoped to repeat the trip at a similar time in the opposite direction but it was not to be. There would have been no call for a tunnel light.

At other times of year this effect was never seen. We imagined the angle of the sun as well as its position relative to the horizon had to be just right to produce it.