An 'upside-down rainbow' smiled down on Chester this morning (April 28).

Becky Holmes spotted the optical phenomenon at around 9.45am from the balcony of ChloBo Jewellery's headquarters at Chester Business Park, where she is currently working as a design intern.

She said: "All the girls at the office were so excited at seeing it that they ran through to the marketing department to make us go see it!

"I couldn't believe it - I've never seen one before and apparently they are extremely rare - hence why I grabbed my camera immediately."

Related story: IN PICTURES: Rare lenticular clouds over Chester

Not actually rainbows

The term 'upside-down rainbow' is a misnomer, however, as they are actually circumzenithal arcs rather than rainbows.

And while they are rare to spot, they occur more often than normal rainbows but tend to be missed because they appear so high in the sky.

According to the Met Office website, a combination of atmospheric conditions must coincide 'just right': "The height, depth and position of the ice clouds must be right as the cloud needs to be at a specific angle convex to the sun.

"The position of the observer is also important since its visibility can vary greatly over short distances."