He expects confirmation of his new role, which would see him advising across Ms Armstrong's portfolio, to come from the prime minister's office 'imminently'. He said: 'My role would be to advise the minister - there's no agenda of my own.'
Mr Wilson is known as a moderniser, and chaired Lewisham's select committee on governance, which received evidence from Ms Armstrong and recommended an elected mayor for the borough.
He was also the council's lead member on best value and has been a researcher for Jack Cunningham MP.
Although the new appointment has forced Mr Wilson to leave his role as deputy mayor, he plans to stay on as a member.