Johnson is the first British prime minister to marry while in office in almost two centuries.
Just days ago, the couple were said to have sent save-the-date cards to family and friends for an event on July 30 30, 2022.
One guest at today's wedding told the Mail on Sunday when asked if the Prime Minister had Wednesday: "You are not barking up the wrong tree".
He said: "I have also spoken.to the Prime Minister who confirms that he knew nothing about such payments until immediately prior to media reports in February 2021".
The Catholic cathedral was suddenly locked down at 1:30 p.m. (1230 GMT) and Symonds, 33, arrived 30 minutes later in a limo, in a long white dress with no veil, both reports said.
Half an hour later, a limousine carrying the bride swept into the piazza outside the main west door.
Classical music was said to be played as they walked down the aisle and exchanged vows.
The couple announced their engagement and news that they were expecting their first child in February a year ago.
It is believed that armed police were standing by for the ceremony.
The controversial makeover of Mr Johnson's official flat above 11 Downing Street by upmarket interior designer Lulu Lytle was said to have cost a six-figure sum.
The pair got engaged in December, 2019, and have a one-year-old baby son, Wilfred.
Lord Geidt suggested Mr Johnson's actions raised questions over whether he had fulfilled his "absolute duty" to set a high standard of conduct as Prime Minister but cleared him of breaching the ministerial code. The proposal reportedly came following his win in the December General Election.
Johnson's last marriage was to Marina Wheeler, a lawyer.
He was previously married at the age of 23 to Allegra Mostyn-Owen in 1987.
The couple had four children but separated in 2018.
Weddings in England are now subject to strict coronavirus restrictions and only up to 30 people in COVID-secure venues are allowed. So many weddings have been delayed and disrupted by covid.
Dancing is not advised, although there is nothing advising against the couple's traditional first dance.
They say Johnson and Carrie Symonds held a ceremony at Westminster Cathedral in central London on Saturday.
Mr Johnson's former chief adviser, Dominic Cummings, claimed in April that the Prime Minister had planned to have Tory donors cover the costs of the refurbishment, a move he considered "unethical, foolish, [and] possibly illegal".