Boris Johnson, girlfriend move into Downing Street

Britain's new Prime Minister Boris Johnson moved into Downing Street on Monday with his girlfriend Carrie Symonds, becoming the first unmarried couple to live in the world-famous address in London.

Johnson, 55, had been living with Symonds, 31, at her flat in south London in the lead up to the Conservative Party leadership contest, the result of which meant he took charge as Prime Minister last week.

"The PM is officially moving in today [Monday] and, yes, his partner will be living there," confirmed a Downing Street spokesperson.

"There won't be any additional cost to the taxpayer,” the spokesperson said, implying that Symonds would not be provided with any publicly-funded staff usually associated with a First Lady.

The move comes as Johnson made his way to Scotland for his first trip to the region since taking office in a bid to "renew the ties" between the UK's four nations of England, Scotland, Wales and Northern Ireland and propagate his vision of Brexit.

The "first couple" will occupy the luxury four-bedroom apartment above No. 11 Downing Street, which is the UK Chancellor’s office. There was some speculation if the historic swap of apartments might undergo a change, given that the new Chancellor, Pakistani-origin Sajid Javid, has a larger family than Johnson. However, the arrangement remains in place, with Johnson set to occupy the larger flat above No. 11 and Javid moving in with wife Laura and four children above the apartment in No. 10 Downing Street.

Johnson is in the process of getting a divorce from his wife, Marina Wheeler, whose mother Dip Kaur is of Indian-origin and gave the former London Mayor a chance to refer to himself as the "son-in-law of India" in the past.

Johnson and Wheeler, who have four children together, had announced their split after 25 years of marriage in September last year.

Symonds, a former head of communications for the Conservative Party, was seen outside Downing Street as her newly-elected Tory leader partner made his first speech outside the famous black door soon after being formally appointed Prime Minister by Queen Elizabeth II last Wednesday.

It ended speculation over whether they would in fact become the first live-in couple to move into the UK prime ministerial residence.

Their relationship had hit the headlines in the midst of the leadership race after neighbours at Symonds’ south London flat called the police over a late-night row and alleged screaming match between the couple. Johnson had repeatedly refused to comment on the incident, saying that he made it a policy not to address personal issues.

It was former Labour Prime Minister Tony Blair who had decided to take No. 11 when he came into power in 1997 as he had a large family unlike Gordon Brown, then UK Chancellor, who was single at the time.

In 2010, when David Cameron became Prime Minister, he also moved into No. 11 because the larger space served his family better. The arrangement continued with Theresa May and Johnson has chosen to keep things as it is.

Some media reports have suggested the new Prime Minister and his partner have plans of adopting a dog to join them at their new address. Any new dog will have to get along with Larry, the official mouse-catching cat resident at No. 10 Downing Street, as well as the Javid family’s dog named Bailey.