Trials of an innovative cooling system for deep-level Tube lines have started, Transport for London (TfL) says.
Following this week's record-breaking temperatures which caused widespread disruption, it is hoped the technology will bring relief for passengers and reduce maintenance costs.
The system uses fans to circulate cool air produced from cold water-filled panels wrapped around the pipe work.
TfL said it would "protect the network against future temperature increases".
Trials are being held on a disused platform at Holborn station with plans in place to further expand it to an active platform at Knightsbridge station, the Local Democracy Reporting Service said.
Though the project has received 70% of its funding from the Department for Transport (DfT), London transport bosses said the expansion of trials and rollout of the technology on other Tube lines depended on securing a long-term funding deal from the government.
TfL officials have until 28 July to hash out a new funding agreement with the DfT following another short-term extension to the existing bailout earlier this month.
If the tests are successful, TfL hopes the panels could be used to cool other deep Tube lines, which has been "prohibitively expensive" in the past.
In 2003, a competition was launched to find a solution to cool down the London Underground.
But two years later, judges were unable to find a winner as none of the 3,500 entries were original or workable.
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