Conservation experts have been using the latest techniques to find out more about Rochester castle’s keep and carry out essential maintenance work.

The team of specialists working with Medway Council have been using techniques similar to abseiling in order to examine the walls, which has given them viewpoints from the castle that have not been accessible for hundreds of years.

A number of data loggers have been fixed to the interior of the keep to collect information over the next three years.

This will help the team to understand the rate of decay to the castle in the modern era, particularly to the surfaces of the fine carved norman stones.

The wireless system allows the information collected to be monitored remotely.

Other tests will include checking samples of mortar and stone, as well as the condition of the core of the massive walls.

Similar exercises have been carried out on York Minster crypt and at Howden Minster Chapter House.

Cllr Howard Doe, Medway Council cabinet member for community services, said: "Rochester Castle Keep is one of the most impressive medieval keeps in the UK and it is important that we maintain it for generations to come. This exercise will help us to understand rate of decay at the castle and what needs to be done to protect it."

Further inspections of the keep exterior will be carried out later this summer.

The project is jointly funded by Medway Council and English Heritage.