The youth, who can not be named for legal reasons, was 17 at the time of the incident in February.

The train driver from Par was hurt when the block was thrown from a bridge into his cab window near Penmere station on the Truro-Falmouth branch line.

Wessex Trains warned other youngsters not to play on railway lines.

The youth was sentenced under the Endangering the Safety of the Railways Act.

Managing director Alan Wilson said: "We are very thankful that our driver has now fully recovered and is back to work. However this incident could so easily have had a different outcome.

"We welcome this sentencing and hope that it reinforces the message that 'the railway is not a playground' and that all actions have serious consequences."