Jason Fraser, the paparazzo-turned-newspaper boss, this morning quit the Express after less than four months in the job.
The executive director said he felt it was "time to move on" and that he had made the decision after "much thought and deliberation".
Mr Fraser's decision to leave is a major setback for Richard Desmond, who bought the newspaper group in November.
Although he has lost many star writers since his takeover, Mr Fraser was his first big signing - contracted to work exclusively for the Express and OK! magazine in a £1m deal.
Mr Fraser - who brokered the first pictures of the relationship between Princess Diana and Dodi Fayed - never settled at the Express and had recently received approaches from another newspapers.
The former photographer is also leaving the board of Northern & Shell.
He said: "After much thought and deliberation I have decided to resign as executive director of Express newspapers and Northern & Shell.
"The four months that I have been here have been an invaluable learning experience with regard to all aspects of newspaper industry.
"However, I have decided that it is now time to move on."
In a statement, Mr Fraser said he was leaving on amicable terms, with Mr Desmond describing him as "a vital force" in the newspaper industry.
It is believed Mr Fraser is quitting because of a series of clashes with management over key decisions.
Friends say he was deeply unhappy when he was forced to take the rap for a set of "exclusive" pictures of the Las Vegas wedding of Chris Evans and Billie Piper.
He had clinched a deal with an Amercian photo agency, Zuma, but to the fury of Express management similar pictures - taken by a different photographer and brokered by a different agency - got into the hands of rival newspapers.
"Jason is used to doing things his own way. He simply didn't like the office politics - they got in the way... He has a very strong personality," said one newspaper source.
Since moving to the Express, however, Mr Fraser's picture scoops have been conspicuous by there absence. Rivals say he only ever had two exclusives that caused envy - a picture of actress Emma Thompson on the beach and a series of Davina McCall on holiday in Mauritius.
Friends say, however, that only about "five minutes of his day" was spent on picture desk work and his main pre-occupation was the commercial direction of the paper, ranging from overseeing promotions to directing the company's latest TV advert.
Mr Desmond said he hoped to continue working with Mr Fraser and that he wished him "every success" in the future.
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