Theresa May was joined by schoolchildren as she illuminated Downing Street by switching on the Christmas tree lights.
The three children, from her constituency of Maidenhead, won a competition to design the Prime Minister’s official Christmas cards.
Mrs May sang Christmas carols with Chloe Hathaway, Amelie Beard and Dexter van Elkan, all aged nine, alongside the Military Wives Choir outside Number 10 on Thursday.
The 22ft Christmas tree was provided by John Junor from the Farr North Christmas Trees in Inverness, after being chosen by the British Christmas Tree Growers Association, who have provided the tree for 20 years.
Military families were also present, with more than a dozen of forces’ families from the Army, RAF, Royal Marines and veterans joining the festivities.
Responding to a reporter who asked if she had a “Christmas wish”, The Prime Minister said: “I wish everybody a very happy, peaceful Christmas.”
Ahead of the switch on, a number of cabinet members were seen leaving Number 10, including the Home Secretary Sajid Javid.
Downing Street said there was not a full Cabinet meeting.
Prime Minister Theresa May said: “I was delighted that so many forces’ families could join me in Downing Street today for the switching on of the Christmas lights.
“While Christmas is a time of celebration, it can be a difficult time for our servicemen and women, many of whom will be serving abroad and separated from their loved ones.
“We are all immensely grateful for their courage and their dedication and I would like to wish them, and their families, a very happy Christmas.”
Richard Stringfellow, vice chair of trustees at the charity Military Wives Choirs and musician in The Band of the Household Cavalry, said: “The festive period can be a particularly tricky time for military families when loved ones are deployed and can’t be home for Christmas.
“Our 74 choirs based across the UK and overseas provide a safe space for women in the military community to come together and sing, share and support one another, which can often be a real lifeline.
“It was amazing to celebrate that fact and perform as part of the Downing Street Christmas tree lights switch-on event this year.”