The damage to the glass protecting a National Gallery painting allegedly inflicted by Just Stop Oil protesters will cost more than £6,000 to repair, a court heard.

Harrison Donnelly, 20, and Hanan Ameur, 22, pleaded not guilty at Westminster Magistrates’ Court on Tuesday to causing £6,445 of criminal damage by allegedly smashing the glass covering a mid-17th century painting of a nude goddess Venus gazing into a mirror held by Cupid.

On the morning of November 6, the duo reportedly hit small orange hammers against the glass protecting the “very famous” painting known as Rokeby Venus, or The Toilet of Venus.

Suffragette Mary Richardson attacked the same Diego Velazquez artwork using a meat cleaver in 1906 at the central London gallery, protesting against the arrest of activist Emmeline Pankhurst.

The artwork itself is not believed to have suffered damage in the incident, the court heard.

District Judge Michael Snow granted them conditional bail until their pre-trial plea hearing at Southwark Crown Court on December 19 this year.

He banned Donnelly, of Sillitoe Way, Nottingham, from entering inside the M25 other than to attend court or meet his solicitors, and Ameur, of Hornsey Road, Islington, was forbidden from entering the London borough of Westminster even to travel through it.

Judge Snow said: “If you come back (to court) for something else I will remand you into custody.

“If you want to be inside (prison) for Christmas commit another offence and that’s what’s going to happen to you.”

Days before the alleged offence at the National Gallery, Ameur pleaded not guilty to aggravated trespass after reportedly storming a performance of Les Miserables in London’s West End, for which she and four others will stand trial on February 5 next year.

Following the hearing, the National Gallery said “minimal damage” had been sustained to the surface of the painting.

“Therefore, it will be undergoing conservation treatment before going back on display.”