Two teenagers who heaved a rock weighing 45lb off a railway bridge, causing horrific facial injuries to a train driver, were given lengthy custodial sentences yesterday.

Worcester Crown Court was told that friends Daniel Ratcliffe and Kevin Clee were seen laughing and joking minutes after dropping the lump of brickwork into the path of two trains last year.

Judge Alastair McCreath ordered Ratcliffe, 17, and 19-year-old Clee to be detained for seven-and-a-half and six years respectively after hearing how train driver Joe Paxton was knocked out when the masonry shattered his windscreen.

Ratcliffe of Broad Street, and Clee of Grasmere Close, both Kidderminster, both pleaded guilty at earlier hearings to criminal damage being reckless as to whether life was endangered.

Sentencing the teenagers, Judge McCreath said the incident, near Kidderminster Harriers' football ground on December 17, could have had even more disastrous consequences.

The court was told that Mr Paxton's freight train, travelling at 50mph and carrying 1,700 tonnes of steel, continued for three-quarters of a mile, passing through Kidderminster's mainline station, before a safety mechanism brought it to a halt.

Judge McCreath told the defendants: "What, between you, you did was to release what was effectively a rock on to the top of a train coming under the bridge you were standing on in circumstances where another train was passing it.

"You did it for no other reason than for your own amusement in circumstances where a moment's thought would have told how very, very dangerous that was. Mr Paxton could have died and the fact that the train went on for a significant distance could have had disastrous consequences."

The judge said the length of the custodial sentences were intended to make it plain that others who behaved in such a way would face substantial punishment.

Prosecution counsel Abigail Nixon told the court that Mr Paxton was en route from south Wales to the Round Oak steel terminal in Brierley Hill, West Midlands, when the masonry smashed into his cab.

Mr Paxton, a 57-year-old father-of-two from Perry Barr, Birmingham, has worked as a train driver for 35 years, but may now have to give up his career.

He suffered severe lacerations, skin loss and fractures to his cheekbone, nose and right eye socket.

"He is still suffering in a lot of pain... on occasions he has been crawling around the floor in agony," Ms Nixon told the court. Mr Paxton also thanked the families of Ratcliffe and Clee, who confessed to relatives about their involvement in the incident, for assisting the British Transport Police inquiry.

Speaking outside court, Detective Sergeant Karolyn Pitham told reporters: "Joe would like me to express his thanks to the investigation team. Joe is pleased with the result of the case yesterday. He would like me to express that he bears no malice to the persons responsible and hopes that they use their sentence to reflect upon the consequences of their actions."

Det Sgt Pitham stressed that the offence could have resulted in a catastrophic loss of life.

"Unfortunately, the rail network continues to attract persons intent on damage, stone-throwing and obstruction offences, all of which have the potential to cause serious consequences to those involved, the travelling public and the train crews," the officer added.