But who is the woman Mr Johnson shares a home with after leaving his wife of 25 years?
The public relations expert had been in the so-called Westminster Bubble for most of her remarkably ascendant career, a high-point being made head of party PR aged just 29.
In 2018, PR Week listed her in its top 10 figures in political communications - second only to No10 chief Robbie Gibb.
Prior to the role, Ms Symonds was a special adviser to Sajid Javid during his tenure as Communities Secretary after a similar stint as John Whittingdale's "spad" during his time at the top of the Department of Culture, Media and Sport.
She also worked on Zac Goldsmith's failed bid to succeed Mr Johnson as London mayor.
Ms Symonds joined the Tory party media machine in 2009, first as a press adviser, then head of broadcast at Conservative Campaign Headquarters ahead of the 2015 general election.
Her association with Mr Johnson dates back to the early years, having worked on his successful re-election bid at City Hall in 2012.
Prior to political PR, Ms Symonds had several jobs in the world of commercial communications and marketing.
She is a senior adviser at Oceana, a US-based environmental campaign group, working with its marketing operation in London.
A profile on the charity's site describes her as being "passionate about protecting the oceans and marine life".
Ms Symonds's acquaintance with the media and national discourse has a familial link.
She is the daughter of Matthew Symonds, a co-founder of The Independent, and Josephine Mcaffee who was one of the paper's lawyers.
Ms Symonds graduated from the University of Warwick with a bachelors degree in theatre studies and history of art in 2009.
She said the serial sex attacker preyed on her after offering her a taxi ride.
Ms Symonds told ITV in 2009 that after drinking one shot of vodka she was "clinging" to the side of his cab.
"The worst thing is not having peace of mind. I'm 99.9% sure that nothing happened to me but I will never know."