The move was announced in an internal message to the Metropolitan Police's 43,607 police and civilian staff last week as part of a project titled 'Bring Your Whole Self to Work'.
The officer has been named only as Callum, or Abi if using a female identity.
"The first time I walked into a Met building as Abi, I was hyperventilating so much I almost passed out. I've done it a handful of times since and felt so happy that I got to be me at work," the officer was quoted as saying by the 'Sun' newspaper.
The officer has been issued with two warrant cards, one in a male name and the other in a female name and the Met said it will be left to the officer, who also has two sets of uniforms, to decide whether to report for work in either male or female identities.
Also Read
It is different from transgender, when a person transitions from male to female or vice versa, sometimes involving surgery.
Chief Superintendent Victor Olisa, the Met Police's head of inclusion and diversity, said: "This project focuses on one aspect of our diverse workforce, but it's just one of the steps we're taking to make the Met a more inclusive organisation."
"We want to get to a place where all officers and staff can bring their whole self to work, whatever their personal background. The diversity of the Met is one of its strengths and we are committed to being a supportive employer that celebrates difference within our workforce.
Disclaimer: No Business Standard Journalist was involved in creation of this content