A Heathrow man has been spared jail despite pleading guilty to masturbating in front of two 12-year-old girls on a train bound for London Cannon Street.

Prasan Mahanty, 42, exposed himself and began masturbating after boarding the train at Orpington on 4 April, 2011.

He walked through the carriages of the train before subjecting the girls to the sex attack.

When the girls realised what Mahanty was doing they left the carriage and got off the train at the next stop.

Despite media appeals, it took police two years to track Mahanty down and they were only led to him after he was was arrested for another offence.

Mahanty pleaded guilty to two counts of engaging in sexual activity in the presence of a child, reported News Shopper.

He was sentenced at Blackfriars Crown Court last week to four months in prison, suspended for two years. He will be on the sex offenders register for seven years.

Detective Constable Andy Parkinson, of the British Transport Police public protection unit, said: "This was repulsive behaviour by a sex offender who sought out children on a busy train for his own gratification.

"Today's sentencing, several years after the offence took place, shows that we will never give up on bringing offenders to justice."