Deep muddy patches of badly waterlogged ground have forced the temporary shut down of most of a World Heritage site.

Jan Tomlin, the National Trust Wiltshire Landscape general manager, described the closure of Avebury henge, stone circles and West Kennet Avenue as part of “quite drastic steps now” to help protect the archaeology so people can enjoy it in the future.

Dr Nick Snashall, archaeologist for the Stonehenge and Avebury World Heritage Site and Briony Clifton, archaeology assistant for the Stonehenge and Avebury World Heritage Site inspect the ground in the Avebury henge ©National Trust/Abby George

It is the first time since the 2001 foot and mouth outbreak that the National Trust has closed the venue and means that nature and history-lovers will be disappointed for a number of weeks.

Fears the waterlogged monument was not only becoming unsightly, and possibly dangerous for visitors, but also potentially risking damage to its archaeology prompted the decision.

Avebury henge and stone circles is a scheduled ancient monument. It is part of the Stonehenge and Avebury World Heritage Site for the outstanding universal value of its Neolithic and Bronze Age archaeology.

An unusually mild January with few frosts and little time for the ground to dry out between wet spells has led to deep muddy patches.

Ms Tomlin said: “We’ve not taken this decision lightly. The National Trusts pledge is to protect Avebury and the other sites we care for, for ever, and for everyone, and it’s a pledge that we take very seriously indeed.

“Hopefully we will be able to open the areas that are closed in a few weeks and by taking these quite drastic steps now, we really can make sure that Avebury will be here for people to enjoy for ever.”

Dr Nick Snashall, archaeologist for the Stonehenge and Avebury World Heritage Site, said: “We know through geophysical surveys and excavation that there is more archaeology under our feet as we walk around Avebury.

“However, the topsoil here is very thin and the archaeology can be quite near to the ground surface. So it’s important that we take steps now to ensure that people walking through the deepening mud don’t damage the site.

“The henge and West Kennet Avenue have been here for 5,000 years, and it’s our responsibility to make sometimes difficult decisions that will ensure it’s here for another 5,000 years and beyond.”

Regular site inspections are taking place with the aim of reopening the henge and avenue as soon as possible, but a sufficient recovery is likely to take a few weeks, the National Trust said.

The National Trust has also imposed restricted access to the parkland at its nearby Dyrham Park site due to the significant damage to the ground caused by heavy rainfall and high footfall. Guided walks are being allowed.