Oxford University students gagged the giant heads outside Oxford’s Sheldonian Theatre shortly before midnight on Wednesday, to protest against plans for a new immigration centre near Bicester.

The students, members of Student Action For Refugees (Star), used white bedsheets to gag the emperors’ heads to symbolise the way detainees were “being silenced”.

The protest lasted 10 minutes before the police arrived and the students agreed to remove the gags.

Demonstrator Aisha Mirza, 19, pictured with Eleanor Mortimer, said: “This was a publicity stunt to draw attention to the plight of detainees like those at Campsfield House in Kidlington.

“The gags symbolised the way that detainees are not being given a proper opportunity to put their case.

“We had no intention of damaging these historic statues — this was a purely symbolic protest.”

Yesterday afternoon, about 50 protesters marched to Bonn Square, where they listened to speeches.