Do the maths......
Correct me if I'm wrong but its a DHL A300 and a Jal 777 346ER
lengths 54.1m and 73.9m respectively. (I could only find specs for the 300.)
In which case measuring the piccies gives respective scales of 1:5.27 and 1:5.15 a difference of about 98%
Which would mean A300 is at difference in distance (not necessarily altitude as its taken from an angle.) 98% (say +/- a percent or so) of the 777
which if they are at 50,000 feet gives a LOS separation of about 1000 feet or so, though you would have to know the angle from the horizontal to get a vertical separation.
Without altitude info. you can't know the separation.
If they are at 5000 feet then people ought to stop supporting West Ham...
but we knew that already.
feel free to check my sums....