The secretive Syrian-born billionaire is seeking currently buyers for a US$3.4bn portfolio of properties thought to be the largest ever put up for sale in the UK.

It is understood that the entrepreneur has hired BH2, the niche property advisory firm, to sell seven assets including the 23-storey Aviva Tower in the City of London Halabi paid US$425m for the 316,000 sq ft tower in 2003, since when the sale is believed to be a "refocusing" and the tycoon was currently buying several other buildings in central London.

It emerged this summer that Mr Halabi had decided to sell his one-third stake in the Shard of Glass, a proposed skyscraper at London Bridge tower at London Bridge which would be the tallest building in western Europe. Halabi had fallen out with partners Irvine Sellar and CLS Holdings, although a legal action between the two sides was settled out of court. Halabi who lives just outside London has one of the most expensive homes in the UK, worth around US$75m.