Elementary my dear Watson.

The case of the purple sky can now be closed.

A never before seen celestial phenomenon that would be christened the Coombes effect? The Aurora making an unexpected and rare appearance at southern latitudes? Even a newly opened trendy nightclub with luminous fountains lighting up the night sky?

Nope.

The main entrance to Huddersfield Royal Infirmary.

It was solved by a friend who found this. I went out looking for the source and found it literally across the road from my house.

I am not expecting to receive the Nobel Prize for physics.

Happy weekend x