A gang of seven youths stole a vital computer part worth £20,000 from Express Newspapers’ mainframe computer in a raid on Ludgate House on Sunday night, losing the Daily Express its second edition.
The part has a resale value of between £5,000 and £10,000.
White, black and Asian youths rushed past security guards and leapt over security gates to get to the computer department on the first floor. A Northern & Shell spokesman said: "It was opportunist high-tech thievery."
An entry guard said: "It was a completely harrowing experience. One moment it was quiet and the next we were surrounded by hooded youths. Everything they did seemed extremely well rehearsed."
The gang pulled out a vital memory board but the first edition was run on so that full distribution was still achieved. A stunned member of the production team said: "They were highly organised."
The youths used a stairwell to exit through the canteen, smashing a window with a fire extinguisher.
The Metropolitan Police said it was called just after 10pm by a security guard and told a large number of youths had forced entry and caused considerable damage to computer equipment. "Security staff were outnumbered and unable to stop them," said a Scotland Yard spokeswoman.
Security staff claimed it was the third attempt on the building in recent weeks.
By Jean Morgan