Court officials locked down the public gallery today in the latest twist in the retrial of battered student protester Alfie Meadows.
Mr Meadows and fellow defendant Zac King appeared for the third time in Woolwich Crown Court on the charge of violent disorder.
But their supporters found the gallery doors locked and Serco security guards insisted no-one could go in.
They later let just six people in.
Court managers are allowed by law to limit access to the public gallery when overcrowding presents a risk to health and safety.
But freelance reporter Glenn McMahon said he counted 10 empty seats in the gallery.
Court manager Keith Reid claimed that the gallery could only hold six people.
"There's only a certain number of seats. It's not a particularly big courtroom," he told the Morning Star.
Presiding Judge Douglas Marks Moore ordered the gallery opened for the afternoon session, after which Mr Reid confirmed to the Morning Star there were 18 seats in the gallery.
He would not say whether the police had asked for it to be closed, saying only that he had to consider security issues.
The stand-off followed attempts by uniformed officers to flank supporters sitting in the gallery at the last retrial.
Mr Meadows, a Middlesex University philosophy student, had emergency brain surgery after he was hit in the head with a police truncheon during a 2010 demonstration in central London against tripled tuition fees.
An Independent Police Complaints Commission investigation was put on hold in 2011 after police charged Mr Meadows.