As Boris Johnson, 55, walked into 10 Downing Street as the new Prime Minister, many eyes were focused on his girlfriend.

Carrie Symonds, 31, watched on from the sidelines as her partner entered the famous residence alone.

A majority of new prime ministers pose for photos with their partners outside the house, but Johnson left Symonds in the cold.

It’s been suggested that this is a deliberate move so that she wouldn’t “overshadow” his moment, according to British media.

Johnson has been married twice before – first to Allegra Mostyn-Owen from 1987 until 1993,

and then to Barrister Marina Wheeler from 1993 to 2018. He has four children with his second wife and has admitted to fathering a lovechild after an affair with Helen Macintyre in 2013.

Nicholas Allan, lecturer in politics at London’s Royal Holloway University, has said that it would be considered “indiscreet” for Johnson to enter the residence with his new girlfriend.

“It is difficult for him to walk into Downing Street with another woman when you are still technically married to someone else. That would be considered indiscreet,” Mr Allen told  Express.

“Boris’s colourful personal life makes the traditional photo call problematic.”

Symonds wore a pink, floral midi dress from Ghost, which retails for £120 ($A215).

The dress “features a high neckline with back fastening and voluminous sleeves and seam detailing at the bodice for definition,” according to the shop’s website.

Johnson has refused to answer questions about whether or not Symonds or the nation’s “First Girlfriend” will move in.

“I just don’t talk about people I love,”  he said last week, according to  news.com.au.    

“They can’t speak for themselves and you drag them into subjects and areas of controversy and discussion that they don’t, in my view, deserve or want.”

Johnson and Symonds have reportedly been living together after the new UK  Prime Minister  confirmed he split from his second  wife last year.