The litigant in person, who cannot be named, has pleaded guilty to assault, criminal damage and causing intentional harassment, alarm or distress and is due to be sentenced.

The judge is being supported and has been offered counselling.

The Family Law Bar Association said that it was “shocked” by the incident.

Hannah Markham, head of the Family Law Bar Association, said: “There hasn’t been another example of an assault like this over the past 40 years. But it does not make this incident any less shocking.

“These moments happen in a second and you don’t always know that they are going to come.

“You get very robust security services at the door of the building, but once you’re in the court we’re trying to make it a comfortable setting and give people the space to give their best evidence. So you don’t want people watching and undermining that process.”

The attack comes in the wake of legal aid cuts, which have resulted in more people representing themselves in court.

Ms Markham said: “When you have representation you have someone who can manage your expectations, talk you through what’s going to happen and help you respond to difficult things.

“But people representing themselves might not understand what is going on.”

A spokesman for HM Courts and Tribunals Service said that “ministers had been in contact” with the affected judge.