Apparently they are 2.5 miles apart and it wasn't reported as a near miss, it happened on Saturday near upton park, the full story is here http://news.bbc.co.uk/1/hi/uk/4660644.stm
I'm quoting a pilot friend of mine who placed this on another forum with reference to the photo and similar questions raised....
"There's at least 1000' separation there, which is all that's required (1000' vertical, or 5nm lateral for aircraft at same alt). The higher aircraft is about twice the length of the lower, smaller jet, and the photo gives no depth perception."