“Essential repair and restoration work” is currently being carried out on an 18th-century grotto on a historic National Trust property in Wiltshire.

The trust said it had closed the grotto at Stourhead House and Gardens, near Mere, to replace the floor. The grotto was built in 1748 for Henry Hoare II, known as Henry the Magnificent.

With more than 370,000 visitors a year, Stourhead House and Gardens is the third most visited National Trust property in Wiltshire.

A section of the pebble floor in the Grotto at Stourhead has been raised © National Trust – Lucy Fenna (Image: ©National Trust Images/Lucy Fenna)

A spokesman said: “The damage to the floor of the grotto was caused by water flowing from the plunge pool inside the grotto into the lake over many years, wearing away the joints of the brick-lined drainage channel.

“The brick drains beneath the gravel floor were also blocked and the force of the water opened up a new, unwanted channel beneath the floor.”

In order to carry out these repairs, the grotto was completely closed on August 5th and will remain closed to the public until Monday, September 2nd.

Visitors in the grotto in Stourhead. ©National Trust Images – John Millar (Image: ©National Trust Images/John Millar)

Tim Parker, Head Gardener at Stourhead, added: “While we are currently carrying out necessary repairs to the grotto, the surveys carried out have shown that these works will ensure that the grotto, which is one of the most popular places in Stourhead, remains protected and will be enjoyed for many years to come.”

At the end of 2022, part of the floor of the listed grotto collapsed, severely restricting access for visitors for safety reasons.

Since then, specialised teams have carried out archaeological investigations to study the substructure and drainage of the grotto building.

Using an environmentally friendly dye, it was possible to observe how the water from the new canal flows underground into the lake.

A key section of drain exposed beneath the pebble floor at Stourhead Grotto. © National Trust – Lucy Fenna (Image: ©National Trust Images/Lucy Fenna)

The grotto’s pebble-covered floor with its concentric circular pattern is a notable feature and the stonemasons have carefully lifted the pebbles to access the drains beneath the floor.

Once the substructure was exposed, further archaeological records were taken to enable the Stourhead team to make informed decisions about any future repair work that might be required.

The Trust explains that new mortar will be prepared and used for the brick canal so that it is sufficiently strengthened for years to come.

The pebbles are then reinserted using a special mortar that needs time to set and harden completely.

The rest of Stourhead House and Gardens remains open during the summer.