Volunteers will continue restoring the grade II listed Croxley Great Barn next month.

The Society for the Protection of Ancient Buildings started work on restoring the 14th century barn in All Saints Lane in 2013.

The success of this work prompted the group to launch an annual event at end of May that will see the barn spruced up by conservation experts and enthusiasts.

Organisers are hoping the community can get behind the project.

Stephen Bull, chairman of the London branch of the Society for the Protection of Ancient Buildings, said: “The Great Barn was built in 1397. It was built before Christopher Columbus discovered America.

“It was standing before the Inca Empire existed in South America.

“When you compare it against other things that have happened in the world, it is quite remarkable how long it has survived.

“It was built by people who would have lived in the area and it will need to be looked after by the people who live in the area.”

Volunteers will begin the clean-up operation while architects draw up plans for protecting the structure of the building.

The barn originally belonged to the Abbey of St Albans where it was used to store grain.

Renovation work was also done in 1973.

“Anyone with enthusiasm” can help, according to Mr Bull.

He continued: “The work we will be doing is well within the scope of amateurs and volunteers.

“We really want people to get hands-on experience helping look after a historic building.

The barn is owned by St Joan of Arc School, High Street, Rickmansworth, and the public were allowed to start visiting it in 2008.

Barbara Owen, who used to teach at the school, convinced her former bosses to allow the public access and the keys to the barn were given to the Three Rivers Museum Trust.

Ms Owen told the Watford Observer: “The school used it for some lessons but that was stopped and then it fell in to disrepair.

“But then it was found by a local historian, David Harding, and he said it was like hiding the crown jewels.

“So many people want to see it.

“It is the only barn built of the seven which is still standing as it originally was.”

Anyone interested can park in the car park at the St Joan of Arc School, on Saturday, May 28.