The division incorporates all of the company's roadside and airport sites in the capital.
JCDecaux London is being promoted as the most "powerful way" for advertisers to reach the capital's most "affluent and influential" audience.
Lambert, who leads a team of six, said the merits of outdoor in London have been undersold, with consumption 68% higher than the rest of the country.
Lambert will continue to report to managing director of sales Spencer Berwin, who said: "London is a showcase for all things that are great in outdoor. If you buy London without Decaux, you only have part of it."
Cornell Tukiri, sales group head UK and International, JCDecaux Airport said by working closely together JCDecaux and JCDecaux Airport can "trail influential travellers throughout their journey" in London using JCDecaux's unique proposition.
The new team's portfolio includes JCDecaux's 20 PrimeTime digital billboards, thousands of six-sheets, StreetTalk phone boxes, 48 and 96 sheets, digital airport sites, Torch and Tower superstructures and iconic sites at the entrance of Heathrow and Gatwick airports.