BT expects to save £1.5 million on energy costs through the upgrade of its network of tunnels under London.

The project will also save 350,000 tonnes of CO2, it added.

The communications firm has awarded a £3.3 million contract for improvement works on 23km of its tunnels to multi-technical services firm SPIE UK.

It will provide BT with cost planning and risk management consultancy alongside design and technical management.

SPIE will install a control system to reduce energy, improve the lifecycle of the plant and technical equipment.

It will also create a new supply and extraction ventilation system as well as cooling devices with dehumidification equipment to remove condensation and moisture from the air.