A German office worker was found guilty on Monday of the savage murder of a British man whose girlfriend he had become obsessed with after they met on a website.

David Heiss, 21, stabbed Matthew Pyke 86 times in a brutal attack after traveling over from Germany and forcing his way into the couple's flat in the English city of Nottingham.

Before he died following the attack in September last year, the court heard that Pyke, 20, had managed to write Dav -- the first three letters of Heiss's name -- on the side of his computer using his own blood, the Press Association reported.

Heiss, who denied murder and said he was acting out of self defense, was given a life prison sentence and told he would serve at least 18 years in jail.

The court heard that Heiss had become infatuated with Pyke's girlfriend Joanna Witton through a war games website the couple ran together from their flat.

He began bombarding Witton with messages of love, visited the couple twice and pestered them until finally they blocked him from their website.

Just days before the murder, he sent an email to Pyke saying he had something I would like to give to you.

It was an act that was born out of obsession and hatred in equal measure, said prosecutor Shaun Smith.

It was obsession for Joanna Witton and hatred for Matthew, because he was Joanna's boyfriend.

Heiss flew over from his home in Frankfurt and made his way to the couple's home. He waited until Witton had left for work before forcing his way in and launching a ferocious attack on Pyke. He returned back to Germany the next day.

I have no doubt that at some stage you decided that Matthew had to die, and that your killing of him involved a substantial degree of both planning and premeditation, which is a significant aggravating factor, the judge Justice Keith said.

Witton and Pyke's family said in a statement: We will never truly come to terms with what happened to Matthew that morning.

It's not fair that we should all have to live like this for the rest of our lives because of one man's actions. He has taken a wonderful, caring, loving young man from all of us.

Detective Chief Inspector Tony Heydon said the brutality of the attack and the clinical planning involved had made it the most harrowing case he had investigated.

Heiss had become so besotted with Joanna that he decided to plan Matthew's murder several days, if not weeks, in advance, he said.

In my view, David Heiss is the most callous, cold-hearted individual I have dealt with.

(Reporting by Michael Holden; Editing by Steve Addison and Paul Casciato)

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