A woman wept as she pleaded with her missing granddaughter to get in touch.

Alex Heamen, 14, disappeared more than three weeks ago and her family is desperate for news.

Grandparents Sandra and John Dunstan travelled from their home in Cornwall for a Press conference in Brighton yesterday.

Mrs Dunstan begged anyone who may be with Alex or may be holding her: "Please, give us a call and let us know she is alive.

"All we want to know is that she is alive.

"You can't believe what we are thinking.

"We wake up each morning thinking today may be the day when we may hear news.

"Then, when night comes and nothing has happened, it is harder still.

"We just need that one phone call."

Alex vanished from her home in Abergavenney Road, Lewes, on September 1.

She has run away before but this time there were no family or boyfriend problems and she was looking forward to returning to Priory School in Lewes for the new term.

The Sussex Police's major crime branch has taken over the investigation and is following up several unconfirmed sightings of Alex in Lewes and Brighton.

She sent a text message to her mother, Tamsin Leverton, two days after disappearing but has not used her mobile phone since.

She was last seen walking on the Palace Pier in Brighton with two men on September 4 and police are examining CCTV footage of the pier and the beach.

Her grandmother, holding her husband's hand, spoke directly to Alex through the media at yesterday's Press conference. She said: "Alex, the first thing to let you know is that you are not in any trouble with the police, social services or family. We can't stress that enough.

"Grampy and I know you love us as much as we love you and that you wouldn't hurt us in any way but we are in the depths of despair and torment, not knowing if you are safe.

"The hardest thing for us at the moment is that we have no idea what has happened to you or where you are.

"We have so many different scenarios going through our heads and just want to know that you are safe and nothing terrible has happened to you.

"Just one phone call or postcard will let us know that you are okay. That's all we ask for.

"We are here to help and support you for as long as you need us."

Mrs Dunstan referred to the recent death of her daughter Gail, Alex's aunt: "Alex, you know that God has already taken away someone very special from us. We really need to know that he has not taken you as well.

"Please, please help us and remember that we love you very much."

Alex stayed with her grandparents for a year when she was ten and Mrs Dunstan said Alex became a daughter to them.

She said: "When Alex ran away before someone told she would be put into a secure unit if she ever did it again.

"We just want her to know that is not true. Nothing will happen. There are no problems whatsoever. We just want to know you are safe."

She said it was possible Alex was "having fun" with someone but it was out of character that she hadn't made some contact with her family. She said Alex was doing well at school and loved dance and drama.

She eventually wanted to work in the care profession.

Alex is white, about 5ft 6in, medium build with blue eyes and dyed medium brown hair.

She is believed to be wearing light blue jeans, a white jacket and black boots.

Anyone with any information is asked to contact Sussex Police on 0845 6070999 quoting Operation Warren.