The brigade is currently overseen by the London Fire and Emergency Planning Authority (LFEPA) which, while funded partially by the Mayor, is a legally separate body with its own members.
LFEPA will cease to exist from the end of March, with Mayor Sadiq Khan becoming responsible for the brigade’s executive oversight. The arrangements mirror the 2012 abolition of London’s police authority and the establishment of the Mayor’s Office for Policing and Crime.
Dr Twycross is currently chair of LFEPA as well as a member of the London Assembly and will become Deputy Mayor on April 1st, subject to a confirmation hearing by the Assembly.
In addition to the new Deputy Mayor role, a new statutory office known as The London Fire Commissioner will be created, with current London Fire Brigade Commissioner Dany Cotton confirmed to take up the post.
Mayor Khan, said: “London’s firefighters, control officers and other Brigade staff work tirelessly to help keep the capital safe and their response to the terrorist incidents and Grenfell Tower tragedy last year was nothing short of heroic.
“Fiona led the London Fire and Emergency Planning Authority with distinction through this hugely challenging time, and Dany has demonstrated incredible strength and leadership of the Fire Brigade.
“I wanted to make my intentions known at the earliest opportunity, and the continuity they provide will be of huge value.
“These changes to the arrangements for oversight of fire services in the capital will provide Londoners with much clearer and more accountable decision making.”
Len Duvall AM, leader of the Labour group on the Assembly, said: “I want to offer my sincere congratulations to Fiona on her appointment.
“In recent times she has helped steer LFEPA through significant challenges, not least in grappling with reduced resources and serious incidents such as the Grenfell tragedy.
“We know her to be a person of the highest integrity who consistently goes the extra mile to serve the interests of Londoners.
“She has proven beyond doubt that she is the best person for the role and will bring with her the necessary expertise and approach to keep our capital safe.”
