Charges have been dismissed against five Extinction Rebellion activists after the police officer due to give evidence at the trial booked a holiday.
Deputy District Judge Vincent McDade said there had been an "abject failure" by the Crown Prosecution Service as has dismissed all charges against the activists at City of London Magistrates' Court.
The court heard that the officer, who was due to be a prosecution witness, was not given enough notice about the date of the trial and had booked to go away.
Five suspects were facing trial for aggravated trespass: Claudia Fisher, 57, from Brighton, Phoebe Valentine, 23, from Brighton, David Lambert, 60, from Gloucestershire, Senan Clifford, 59, also from Gloucestershire, and John Burrage, 42, from West Wales.
Deputy district judge McDade said: "There has been an abject failure by the Crown Prosecution Service to ensure that this case has been properly managed."
He said the police officer who was to appear for the prosecution was required from the outset.
"Had the CPS acted efficiently and warned the witness as soon as possible after the case management hearing on November 7 this matter would proceed today with that witness giving live evidence," he said.
The judge said the police officer - the officer who carried out the arrests - was considered a "vital witness to establish the lawfulness or otherwise of the arrests".
He said he had "no option but to dismiss all matters against the defendants".
