wrote:

pretty clear in the west, cloudy to the east, and from where i was in
west london i could see very purple sky to the north as you mentioned
but to the south-east there was an amazing band of cloud above the
horizon that was fiery yellow. above this, for a very brief period,
was a very narrow band of cloud of a green hue which i've never seen
before. i've seen references on the web to the 'green flash' but that
seems to be in clear skies at the moment of sunset - this was nothing
like that.

Probably an iridescent cloud - the angle between it and the sun would be
a telltale indicator. Have a look at Les Cowley's website.

http://www.sundog.clara.co.uk/atoptics/phenom.htm

It isn't the right time of year for rare nacreous clouds, but you can
get other more common types that show iridisation most commonly green or
pink (sometimes banded if you are lucky). If you post the picture it
would be easier. Worth bracketting exposures to capture clour colours.

Regards,
Martin Brown