Student accommodation specialist Urbanest has paid the developer £25m for a car park on the site to build a high-rise block of 454-rooms.
This will trigger work start on the 3-acre redevelopment site in Nine Elms where CLS plans a 1.58m sq ft scheme, which will include two 50-storey residential towers of 513 flats.
The plans also include a large hotel and four screen cinema with surrounding shopping and cafes.
The car park site in Vauxhall has planning consent for a 30-storey student building, which Urbanest now expects start work on early in 2016, implementing the planning consent for the whole of the Vauxhall Square scheme.
Sten Mortstedt, Executive Chairman of CLS , said: “We are delighted to have concluded this transaction with such a well-respected student operator, and look forward to our vision for Vauxhall Square beginning to become a reality.
“Urbanest will bring excitement to the area and further enhance a vibrant community feeling in Vauxhall.”