London:
England's Queen Elizabeth II made a show-stopping appearance live on the BBC news today as she officially opened the corporation's new headquarters, pressing ahead with engagements as her husband Prince Philip awaited exploratory surgery.
At one point, the 87-year-old monarch appeared directly behind the television newsreaders who were live on screen as she toured the new wing of Broadcasting House in central London.
The sovereign - whose husband was in hospital for an abdominal operation a few streets away - walked through the packed newsroom directly behind live presenters Julian Worricker and Sophie Long.
They turned to see the head of state watching them and quickly acknowledged her as the guided tour came to a halt, with staff breaking into applause.
"That is one of the most bizarre bits of television that the BBC has produced for some time, as the queen makes her way past the BBC news channel studio," said Simon McCoy, who was presenting coverage of her visit.
Moments before, the sovereign had officially opened the high-tech new wing to the 1932 art deco building, which brings all the British Broadcasting Corporation's news operations under one roof.
"It is a great pleasure to visit the BBC today and to see it in its new home," she said, in a live broadcast from the Radio 4 studios.
"I remember first coming to Broadcasting House with my father the king and my mother and sister, shortly before the war," she said.
"I came again with the Duke of Edinburgh just before the coronation in 1953. I was struck then, as I am now, by the sheer pace of change which has transformed your industry over the past 60 years - years during which broadcasting has enriched our lives in so many ways. I hope this new building will serve you well for the future and I am delighted to declare it open," she said.
The applause from staff listening throughout the building could be heard.
Then, for the first time, the BBC aired a sound recording of her first visit to their studios in 1939.
Along with her parents king George VI and queen Elizabeth, and her sister princess Margaret, she was taken into a control room, played some sound effects and invited to experiment with recording technology.
The young princesses, who turned 13 and nine that year, could be heard chatting and giggling.
Earlier she watched Irish soft rock band The Script perform David Bowie's "Heroes" live on Radio 1.
She had an extended chat with veteran BBC presenter David Dimbleby, whose father Richard commentated on her coronation, 60 years ago this week.