Hammersmith Bridge has been wrapped in foil to prevent it overheating as temperatures rise.
Engineers were spotted covering the chains on the Grade II listed, 135-year-old structure with silver-coloured foil to protect it ahead of the potential record-breaking heatwave heading to the UK.
At night, a £420,000 temperature control system is switched. The measures are designed to keep the bridge open as the capital is forecast to have temps topping 35C next week.
The chains are anchored to the river bed and are maintained to stay at a temperature of 13C in the summer, with orders to close the bridge if any of the chains reach 18C.
Sebastian Springer, the engineer who is leading the project, said: "The safety of the public is our first priority.
"The temperature control system allows us to track weather spikes and maintain a constant temperature. As we deal with the current extreme heat, we are also coming up with innovative solutions to keep the temperature within the threshold."
Two years ago, prior to the cooling system being fitted, the bridge had to close down due to the heat.
The introduction of the metal foil comes after the Met Office issued an amber weather warning from Sunday 17 July to Tuesday 19 July, saying the conditions could pose a ‘danger to life’ or lead to serious illness.
Met Office said: “Some exceptionally high temperatures are possible during Sunday and could lead to widespread impacts on people and infrastructure.
“Population-wide adverse health effects are likely to be experienced, not limited to those most vulnerable to extreme heat, leading to potential serious illness or danger to life. Government advice is that 999 services should be used in emergencies only; seek advice from 111 if you need non-emergency health advice.”
The warning continued to say that ‘substantial changes in working practices and daily routines’ were likely to be required.
It said there could also be an increased risk of water safety incidents due to ‘significantly more people’ flocking to coastal areas, lakes and rivers to soak up the sunshine, while delays on roads and road closures are possible – as are delays and cancellations to rail and air travel.
These delays, the meteorological service said, could pose ‘significant welfare issues’, even if hold-ups are only ‘moderate’.
It warned: "Some exceptionally high temperatures are possible and cumulative effects of warm nights and hot days are expected to bring widespread impacts to people and infrastructure.”