Elspeth said:
That was also the case for the two or three years of her considerably more serious affair with Dr Khan, but they never got round to murdering her for it.
Excellent point.
To Queen Katharine, even <if> 'they' had wanted to do away with stubborn, too-popular Diana, 'they' would never have resorted to a difficult, if not risky, to accomplish faux accident like the one she died in.
Why? Because it would have been way, way easier, and more effective, to use a different methodology like poisoning her and then leaving the body in i.e. a posh hotel bath tub with a couple of empty pill bottles nearby as well as an empty bottle of vodka. It would have looked like a suicide, a la Paula Yates. It would have been easier to get away with, because they could have used the argument that Diana was lonely and had other psychological issues.
You conspiracy believers give way way too much credit for government organizations such as the British Mi5. These organizations are not the Borg, rather an amalgam of human talent, and as we all know from working in organizations, most companies and government agencies aren't nearly as well organized as some of us would like to believe.
Also, as for the motive, there really wasn't any, as Elspeth and Trinny pointed out. Diana was a great woman, but let's not overestimate her post-divorce importance to Britain. She was a socialite, and an effective one, but killing this high-profile tabloid favorite would have been an extremely risky thing to get away with, it wouldn't have been worth it.
And, Queen Katharine, I don't mean to jettison the 'way you feel' about this, but what exactly do you base these feelings on? Who, in other words, would be your prime suspect?