A charity could stump up £10,000 for information which leads to the identification of a man who allegedly assaulted two Harpenden teenagers.

CrimeStoppers is offering the reward - a portion or all of £10,000 - and has re-released an e-fit of somebody they would like to speak to in connection with the crimes.

The reward and appeal coincides with the 20th anniversary of the crimes which took place in Harpenden on April 7 and June 19, 2002.

During the April 7 incident, a 16-year-old was walking along Piggotshill Lane when a man grabbed her.

The man dragged the victim into a nearby field where he sexually assaulted her, and forced her to perform sexual acts on him.

The offender is thought to have been using a silver Vauxhall Astra with a C or D registration.

During the June 19 incident, a girl, aged 17, was walking along Wheathampstead Road when a man forced her into a small red car.

According to CrimeStoppers, the offender drove down Piggottshill Lane and took her to a wood where he forced her to perform sexual acts.

The offender is thought to have been using a car a similar size to a Vauxhall Astra, with an "M" registration plate.

It is thought that the crimes were committed by the same person.

Annabelle Goodenough, CrimeStoppers South East Region manager, said: "These are awful, heinous crimes which should never have happened.

"Two innocent children 20 years ago went through terrible ordeals, and they have had to grow up without anybody facing justice for the severe harm caused to them.

"We know it can be difficult to speak up about someone you suspect may be involved in a serious crime, especially if they are close to you.

"This is why our charity is here to help."

Anybody with information can contact the charity on 0800 555 111 or online (https://crimestoppers-uk.org/).

The person is described as being between 5 foot 7 inches and 5ft 9in tall with dark hair, and aged in his late 30s - now in his late 50s.

No person has ever been identified as the alleged double sex offender, despite past BBC Crimewatch and Hertfordshire Constabulary appeals.