Public access will soon be re-opened to the former Edinburgh Royal Infirmary site which now features two new roads, to be called Simpson Loan and Nightingale Way.

The first office staff, meanwhile, are due to arrive for work by the end of the month at the glass-fronted building just completed on Lauriston Place.

By then access to the development from Middle Meadow Walk will also be available, next to the first blocks of flats that will be occupied. And by the end of the year the first shops should be open at the Middle Meadow Walk entrance to the site.

First Minister Alex Salmond was tonight due to officially launch the £450 million development. It is expected to take another five years to complete the scheme, which will eventually boast more than 900 homes, 300,000sq ft of office space, cafes, bars and restaurants, a boutique hotel, and a major public square.

Of the 175 homes put up for sale in the first phase of Quartermile more than 100 have already been snapped up, including four luxury penthouses costing up to £1.5m each. All 175 are expected to be sold and fully occupied by the spring.

Law firm Maclay Murray and Spens has sealed a deal to take about half the space in the flagship office block, Quartermile One, which is playing host to a gala VIP reception and dinner tonight.

The development - a joint venture between housebuilder Gladedale and the Bank of Scotland - has been promoted as far afield as Hong Kong, Beijing, Singapore and South Africa.

Jim McIntyre, managing director of Gladedale's development arm, Gladedale Capital, said: "The vision of a new urban quarter at the heart of Scotland's capital is now coming alive. We're delighted to finally take the covers off the first of these buildings and show the world our vision for a groundbreaking, though sympathetic, redevelopment of this historic site.

"The site has been closed off to the public for more than five years now, but it will be a lot more opened up than before. We've reached a very significant point in the development."

Work on the 20-acre site began more than four years ago after the then Scottish Executive backed an initial scheme.

However, the developers asked the council to make a number of major changes to the scheme, including demolishing the 19th century Red Home building in the heart of the site, which happened earlier this year.