Police and emergency services were called to the Mandeville Road site next to Northolt Tube station on Saturday just after 10.30am to rescue the workers.

The five men were recovered after an hour with one hospitalised, and the others treated at site for minor injuries and then later sent to hospital for checks.

All construction work has now halted at the site while the Health & Safety Executive investigates the incident.

Skanska Costain Strabag JV are responsible for the design and construction of the Mandeville Road ventilation shaft and headhouse.

A spokesperson for HS2 said: “We are working with our construction partner and the Health and Safety Executive to thoroughly investigate the cause of this incident.

“To facilitate this, all construction work at the site has stopped.

“Four people involved in the incident have been discharged from hospital. One individual remains in hospital and is receiving treatment for a back injury. We wish them well with their recovery.”