I gave you the example of India (which derives its court system from the UK), it's not my fault you didn't like it.
A small percentage of the media may be involved in gossip, but when it comes to political corruption, we need to have complete transparency, without any compromises.
You need transparency of result, but you don't need it immediately. Legal proceedings can feature a lot of untruths as well, some of which could cause great harm. The reality is that courts in civilized countries deal with sealed evidence/testimony on a regular basis for a variety of reasons, and this doesn't substantially impede the course of justice even though it may occasionally be perverted. I'm highly skeptical of arguments that reject any possibility of compromise, because they tend to assume the outcome will be a perfect process.
Using the threat of economic consequences is a horrible reason to enable politicians to usurp power from the free press.
I think you're projecting your imagination about what the case involves a bit here. I really don't see enough details to be sure. What if the allegations under seal turn out to be baseless or inaccurate, for example? Is the satisfaction of immediate total transparency worth the damage that may accrue during a multi-year legal proceeding before the court issues a verdict? After all, you can punish guilty parties following a conviction, but it's very hard to repair an innocent person's reputation.
Where senior officials of other countries may be involved in a case, in a variety of capacities from potentially culpable to entirely innocent, are you willing to risk plunging someone else's country into political instability before you've had time to fully assess the evidence? What if the people of the country think the legal proceeding is an attempt to meddle with their internal politics, whether or not this is actually the case?
I strongly disagree with you about transparency being an unalloyed good or a panacea for social ills. Within reasonable limits (and I think a 5-year period for a complex legal proceeding may meet that standard) it can be appropriate to employ judicial discretion.
Obviously, we're not going to agree about this, but I'll put a note on my calendar to follow it up in 2019 and see what the big secret was.