A new British Airways steward mistakenly activated the emergency slide moments before take-off in a first-day error that reportedly cost the airline £50,000.

The new crew member triggered an evacuation procedure by opening an escape door on a flight that was preparing to take off from Heathrow to Lagos.

The Sun reports his action prompted an inflatable evacuation slide to be deployed from the side of the plane, meaning it could no longer be used.

Passengers were told they faced a four-hour wait for a replacement aircraft and the mistake cost a total of £50,000 including the replacement slide, missing a take-off slot and switching aircraft.

According to reports, passengers took off on the replacement flight with the same crew, minus the new steward.

BA is looking into the incident and has issued a statement saying: “The aircraft returned to stand and customers disembarked normally.

“We apologised to customers for the inconvenience caused, provided them with refreshment vouchers and arranged a replacement aircraft so that they could continue their journey as planned.”