A device that measures ultraviolet radiation levels in the centre of London has been installed on the roof of St Thomas' Hospital.
The Solar Ultraviolet Monitoring Station has been installed to measure the sun's strength and the number of hours of sunlight.
Dr Andrew Coleman, a medical physicist at Guy's and St Thomas' NHS Foundation Trust, said: "This is an exciting opportunity for us to have such pioneering equipment at our hospital and to contribute to a UK-wide network of monitoring stations.
"The north wing roof of our hospital is flat, and is not obstructed by any tall buildings, so it is perfect to measure the sun as it offers a complete view of the horizon.
"The aim is to collect data to help determine the impact of climate change on groundlevel UV levels."
The UV station installation was coordinated by Dr Fiammetta Fedele, a senior physicist at Guy's and St Thomas', who has been collaborating with Public Health England on this project.
Dr John O'Hagan of Public Health England said: "We are delighted to add central London to our solar UV monitoring network and we are very grateful for the support provided by staff at St Thomas'.
"The London site complements our other systems operating across the UK from Camborne in Cornwall to Lerwick in the Shetland Islands."
Researchers at Guy's and St Thomas' and King's College London will use the UV station for research purposes. The Medical Physics Department at Guy's and St Thomas' currently carries out research in photodermatology, the effect of light on skin disease, and runs a UKAS accredited laboratory calibrating UV instruments for phototherapy centres around the UK.
Data from the station will soon be displayed on a website for the public to view.