You might at least have got the name right - It was Princess Diana, not Diane, and comments such as "money is being allowed to buy revenge" are just silly.
The whole point of an inquest is precisely because the deceased cannot have their say, it's an inquiry into the manner of a person's death. An inquest must be held in each case where a death was violent or unnatural, sudden and of unknown cause, or if the deceased died in prison, or in police custody.
In this case the inquest is not a perversion of the course (not 'cause') of justice. The relatives and friends of the deceased have no say in whether an inquest takes place, it's the law, and the coroner's decisions are made in the light of what the witnesses say under examination. People can be compelled to give evidence at an inquest, but their testimony is subject to what's called the priviledge against self-incrimination.
There have certainly been criticisms of the rules under which coroner's inquests are conducted, and there's a body of opinion that says coroners should have much wider powers, that relatives of bereaved people should be allowed to make a greater contribution to proceedings, and that there should be full-time coroners. A draft bill incorporating these reforms (and others)was published in 2006.
None of that means that inquests conducted under the current system are perverting the course of justice - inquests are not about justice in that sense, nobody is accused of anything and on trial. There's a jury in this case, but most inquests don't have one, and a coroner is only required to appoint one in certain circumstances.