London Mayor Boris Johnson has appointed the Conservative leader of Wandsworth Council as his new chief of staff, following the death of Sir Simon Milton.
Edward Lister, who has led the council since 1992, will also become deputy mayor for planning.
Former chief of staff and deputy mayor Sir Simon, a former Westminster City Council leader, died suddenly last week at the age of 49.
Mr Lister will manage the mayor's budgets and relations with boroughs and seek to ensure that the "right balance is struck between much needed development and respecting the city's skyline and character".
Mr Johnson said: "Edward has the perfect combination of experience, character and expertise to help me lead this city out of recession and harness the unique opportunity of the 2012 Games to secure London for another generation as the best big city in the world.
"We will always mourn the loss of Simon Milton. The greatest tribute we can pay him is to deliver in the areas that mattered so much to him and improve the lives of Londoners in the great city that he loved. Edward Lister shares that goal."
Mr Lister said: "I'm delighted to be joining Boris Johnson to take forward his ambitious vision for this great city.
"My focus in Wandsworth has always been on improving the quality of life of our residents. I now relish the opportunity to do that on a London-wide basis."