Mystery surrounds the origin of unusual contrail patterns spotted in the skies over Grimsby yesterday – after both the RAF and US Air Force say they were not caused by their planes.

As reported at – where you can view pictures and video footage of the trails being made – the newsroom was flooded with calls about the unusual display.

Philip Greenfield, of Waltham, was first off the mark, saying he had been "delighted" to see "heart-shaped" patterns appearing in the skies over Waltham Windmill.

But, as quickly as they were formed, the wind dispersed them, leaving more circular shapes to linger overhead.

To read more and view the video, click here.