The main London office of Deutsche Bank is nearing a 250 million pound sale to U.S. money manager Invesco , a source close to the deal told Reuters.

The sale of the building on the corner of London Wall and Old Broad Street in the City financial district by German open-ended fund KanAm follows legal changes in Germany that have sapped demand from investors for such funds, forcing some to shut.

Invesco Real Estate has 20.6 billion euros (16.26 billion pounds) of assets worldwide, according to its website, with European offices in London, Paris and Munich. It was not immediately available for comment. KanAm declined to comment.

KanAm, which plans to liquidate by 2016, has already sold two London office buildings housing the European Bank for Reconstruction and Development and law firm Olswang for about 570 million pounds to Malaysian investment fund Permodalan Nasional Berhad.

It owns about 50 properties in nine countries valued at around 6.3 billion euros ($7.75 billion). Its remaining London asset will be a block occupied by Thomson Reuters in the Canary Wharf financial district.

Investors are supposed to be able to withdraw money at any time from open-ended property funds, making them different from closed-ended funds and meaning they have been popular among German savers in recent years.

However, some German open-ended funds, in which about 85 billion euros is invested, temporarily closed in recent years to prevent a rush for the door as the weak economic conditions pushed property prices down.

Legal changes in Germany attempted to protect smaller private investors from such closures by making it difficult for larger investors to exit at short notice, which has also had the effect of sapping demand, meaning some funds will close.

The Deutsche Bank deal would be the latest in a string of large office blocks sold on the back of central London's perceived safe investment status.

The deal was first reported by UK trade magazine Estates Gazette.

(Reporting by Tom Bill; Editing by Mark Potter)