David Gray, a very successful JP Morgan investment banker has thrown away his career by stalking his beautiful colleague Daniela Rausnitz.

David Gray, 28, is almost certain to be fired from his prestigious position at JP Morgan after a passionate affair became an uncontrolled obsession.

The young and wealthy American analyst was yesterday convicted of harassing Daniela Rausnitz, 25, after she transferred to the global finance giant’s London offices to escape him.

David Gray, a very successful JP Morgan investment banker has thrown away his career by stalking his beautiful colleague Daniela Rausnitz

David Gray deluged Daniela Rausnitz with hundreds of texts, emails and phone calls as he repeatedly flew across the Atlantic to pursue her when their one-year relationship turned sour.

He used his old key to get into her Chelsea flat, falsely said his sister had died and even claimed he was critically ill in a desperate effort to attract her attention.

Daniela Rausnitz told police David Gray planted a tracking device in her phone and hacked her email, leaving her afraid that his campaign would never end.

When officers confronted David Gray at a Park Lane Hotel where daniela Rausnitz was hiding with her family he told them he was an agent for the Israeli secret service.

Even on the eve of his trial David Gray was accused of breaching his bail by turning up at the same Notting Hill restaurant as his former lover.

David Gray deluged Daniela Rausnitz with hundreds of texts, emails and phone calls as he repeatedly flew across the Atlantic to pursue her when their one-year relationship turned sour

West London Magistrates’ Court heard the couple met while working in adjacent cubicles at JP Morgan’s investment banking division in New York. David Gray, a graduate of Ivy League Cornell University, had been working for the firm since 2004.

Daniela Rausnitz worked as an unpaid intern before completing her studies at Duke University, ranked as one of the best in the world, where she set up a high-profile organization dedicated to supporting women in business.

When she returned as an employee she began an affair with David Gray, despite the fact he was married. In a strange twist, their relationship was cemented after she confided that she was being sexually harassed by a senior banker at the firm.

The court heard they were at one point “very much in love with each other” as David Gray considered leaving his wife.

But his behaviour became stifling and when Daniela Rausnitz transferred to London to further her career and put distance between them, he followed her.

The tipping point came in August as David Gray flew to London four times and subjected his victim to a relentless barrage of visits and messages.

David Gray was extremely jealous after discovering she had a new boyfriend during one visit and caught them together at her Chelsea flat.

At one stage David Gray sent Daniela Rausnitz 176 text messages and 23 emails over just 16 hours. He even used his key to enter her Onslow Gardens home and take two candlesticks that belonged to his grandmother.

Daniela Rausnitz accused him of trying to change his flights so they were on the same aircraft, putting a tracking device in her bag and breaking in to her email account.

David Gray collapsed in front of her at Heathrow Airport –something she accused him of faking and which he said was brought on by stress.

And in a bizarre confrontation at the Intercontinental Hotel in Park Lane, David Gray was arrested after telling police he was an Israeli secret service agent.

Carrying two bottles of whisky and Cuban cigars, David Gray said he travelled to the hotel to apologize to Daniela Rausnitz and her father.

David Gray told a police officer that he had received tapes of conversations recorded by a hidden bug under the bed at her home and urgently needed to speak to her.

Speaking in his defense, David Gray admitted the story was a complete lie which he concocted in a desperate attempt to evade arrest.

David Gray also admitted claiming falsely that his sister had died and that he was seriously ill in a Paris hospital after an accident. He described himself as a “broken man”.

David Gray’ solicitor Dan O’Callaghan described him as a “pathetic lovelorn fool” who was sent “mixed signals” by the victim.

Daniela Rausnitz wept in court as she described how David Gray’s actions left her scared, unable to sleep and forced her to take a leave of absence from work.

In a statement, Daniela Rausnitz said: “His erratic and obsessive behaviour began to frighten me and I was hopeful that moving to London would put an end to it. Unfortunately it escalated.

“His unwarranted, unprovoked and unrelenting actions have caused me extreme distress.”

Sentencing David Gray to a conditional discharge at West London Magistrates’ Court, District Judge Andrew Sweet said Gray could face a serious penalty if the harassment continues.

The judge said David Gray will be arrested if he contacts Daniela Rausnitz by any means and then visits Britain.

The court has no powers to stop David Gray contacting his victim from America but can arrest him if he returns having done so. David Gray is free to come to Britain if he does not contact Daniela Rausnitz before or during the visit.

JP Morgan declined to comment.