While looking eastwards along the river Thames at a time nearing sunset and observing the first signs of the rising earth shadow and the belt of venus, I also got an unexpected verification of Isaac Newton's Rainbow experiment. The sun is in a low position shining directly at 20 Fenchurch Street, (that is the concaved shape building that looks like a walkie talkie). It has split into its component colours.

The sun at this time was a red/orange colour, becoming redder with time - presumably blue light starting to become more scattered yet there appears to be blue light being reflected of the building.

The other thing I noted was that the diffraction pattern suddenly happened at a particular time, perhaps corresponding to a particular angle. In the half hour leading up to this point you could see a reflection of a round sun sliding down the building - going from bright yellow in colour to a more candle flame orange, becoming a redder orange, until the round shape disappeared and there was just a patch of red/orange colour. When it came to within 7 minutes of the expected sunset time the patch became a diffraction pattern.

Canon Powershot HS Sx40

Slight adjustment in highlight/shadow exposures such that highlights weren't washed out and the shadows have some detail.