A Court of Appeal judge said the "core" of a major terrorism trial will be held in secret as "this case is exceptional."
Lord Justice Gross, one of three judges who made the decision, said:
We are persuaded on the evidence before us that there is a significant risk - at the very least a serious possibility - that the administration of justice would be frustrated were the trial to be conducted in open court; for what appears to be good reason on the material we have seen the Crown might be deterred from continuing with the prosecution.
The trial is due to start at the Old Bailey on June 16.
More top news
More than 1.85 million people have called for the US president's visit to be watered down to avoid causing "embarrassment" to the Queen.
Jim Mattis arrived in Baghdad on the day after US-backed Iraqi forces launched an operation to reclaim Mosul from IS.
The scale of the blood poisoning disease sepsis is "far worse" than previously thought thanks to a "crippling" lack of data, a study says.