The Queen hosted NATO leaders for a reception at Buckingham Palace on Tuesday evening.
A choir ran through Christmas songs as guests began arriving, including Hark the Herald Angel, Walking in a Winter Wonderland and We Wish You a Merry Christmas.
Later the NATO country leaders adjourned to Downing Street for a second reception, this time hosted by Boris Johnson. They were greeted by a school choir singing carols as they posed outside No 10 and a festive tree.
A meeting of NATO leaders is being held in London on the 70th anniversary of NATO"s founding.