Smoke Ring or UFO?

Georgina Heap, the 16-year-old girl who recorded the video of the ring, told the Mirror:

I looked up at it and thought 'what the hell?', it was amazing. It was just floating there like a cloud and then it disappeared. It wasn't birds either.

Link to the Mirror Article.

This happened over Leamington Spa, Warwickshire in England. Weather experts say that there were clear skies and no fires at the time of the sighting, so we can assume they are just as confused as we are...

Link to Article on Sploid.

In either case, it is a baffling find and leaning more towards UFO than anything else...

UPDATE: According to a poster on Sploid(named "twennyone21")
It was caused by an explosion of a transformer. Here is a similar video from after a transformer explosion.

take it easy ;)