Condolences to all affected by this terrible accident.
Speculation is a positive thing in my view so long as it refrains from negative or offensive assumptions on deceased aviators abilities. Clearly nobody here was involved in the accident on sunday so I doubt very much whether anyone can catagorically state that a poor lookout was the overriding factor in this accident. Although 'lookout' may play a part one must also realise that any number of other factors could be involved including airspace classification, ATC limitations and not least a bit of sunshine on a weekend bringing many flyers into the busy UK skies. My sources tell me Coventry was extremely busy on sunday.
To insinuate the pilots involved were not maintaining a proper lookout is... well... I refer readers to the red writing at the bottom of this page! Constant bearing = constant danger and as the above poster states, you probably won't spot it until it's too late.
My thoughts are with all those affected by this awful accident.
RIP fellow aviators.
VFE.