(Daily Mail)

Boris Johnson and his girlfriend Carrie Symonds are engaged and expecting a baby in early summer, they announced tonight.

On her Instagram this evening, Ms Symonds shared an intimate photo of her and the PM and wrote: ‘I wouldn’t normally post this kind of thing on here but I wanted my friends to find out from me.

‘Many of you already know but for my friends that still don’t, we got engaged at the end of last year… and we’ve got a baby hatching early summer.’

The Prime Minister has five confirmed children, however, this will be the first child born to his 31-year-old partner.

Mr Johnson recently finalised his divorce with estranged wife Marina Wheeler, with whom he has two daughters and two sons.

While he was still married, he began dating PR guru and Tory adviser Ms Symonds, and the couple are believed to have been dating for close to two years.

A spokesperson for the couple said tonight: ‘The Prime Minister and Ms Symonds are very pleased to announce their engagement and that they are expecting a baby in the early summer.’

Ms Symonds and Mr Johnson, who live together in Downing Street, recently arrived back from a luxury Caribbean vacation in Mustique.

The couple’s relationship has been firmly in the public spotlight, and a row in her Camberwell flat during last summer’s Tory leadership election wobbled Mr Johnson’s bid for the top job.

Yesterday, it emerged Ms Symonds had hired a media professional to handle her communications and help on her campaigns as she moulds into the role of the UK’s first lady.

Ms Symonds is the first unmarried partner of an incumbent British prime minister.

She has largely kept out of the public eye since Mr Johnson, 55, took the reins of government in July.

She was scarcely seen at the PM’s side on the general election campaign trail but waved with her soon-to-be husband on the steps outside the famous black door following the Conservatives thumping victory.

The couple chose to live at the larger four-bedroom flat at No 11 Downing Street instead of the smaller two-bedroom official residence at No 10.

The couple already share a dog, Dilyn, together with the PM saying that he helped keep his stress down during the election campaign.

Previous prime ministers David Cameron and Tony Blair both had Downing Street babies, Florence and Leo, respectively.

Former Scottish Conservatives leader Ruth Davidson was one of the first to congratulate the Prime Minister on the news.

Re-tweeting the news, she wrote: ‘Congratulations to Boris Johnson and Carrie Symonds.’

Ms Davidson, who had been critical of Mr Johnson during the European referendum campaign, stepped down as Scottish leader last year to spend more time with her young family.