LONDON (BLOOMBERG) - A London apartment that will overlook Buckingham Palace was bought for 20 million pounds (S$42 million) before construction of the building has started, the project's developer said.

Northacre Plc, the luxury-apartment developer 70 per cent owned by Abu Dhabi Financial Group LLC, has sold 29 of the 72 luxury residences at No. 1 Palace St. in six months, Chief Executive Officer Niccolo Barattieri di San Pietro said in a conference on Wednesday. He didn't identify the buyers.

"We haven't done any marketing, it's been word of mouth," the CEO said. The buyers are from the Middle East, Africa, Russia and the U.S., including some from Silicon Valley, he said. "It's a mixture of old and new money."

London's most expensive homes and apartments fell 11.5 per cent in the third quarter from a year earlier as an increased transaction tax damps demand. In addition to the Palace Street project, the Abu Dhabi investor plans to build 300 to 350 apartments at the former headquarters of New Scotland Yard in the Victoria district.

The Palace Street apartments near Queen Elizabeth II's London residence fetched 2,950 pounds to 5,000 pounds a square foot, the Northacre CEO said.

"The actual craftsmanship and standards are uniform across the whole building," he said. But a residence that "has 12 windows overlooking the gardens of Buckingham Palace with 4.5- meter ceilings? You have to pay a premium for that."

Abu Dhabi Financial Group bought the site in 2013 in a 310 million-pound financing deal. Northacre is demolishing an existing property to make way for an apartment building set to be completed in early 2018.

The Middle East investor acquired New Scotland Yard, the headquarters of London's Metropolitan Police since 1967, for 370 million pounds in 2014. Northacre is waiting for its plans to be approved, Barattieri di San Pietro said.