The Queen has met a host of BBC stars at Broadcasting House in central London on the day before her birthday.
The monarch chatted to broadcasters including Sir Terry Wogan, John Humphrys and Chris Moyles.
Earlier, she heard a debate about world politics during a visit to the Royal Institute of International Affairs at Chatham House.
Both organisations were granted their royal charters in 1926, the same year the Queen was born.
The visits come on the day an official photograph of the Queen by Lord Snowdon was released to mark her 80th birthday.
The Queen has been celebrating her birthday with a variety of events spread over the week.
Sir Terry said afterwards he had been asked by the Queen how long he had worked for the BBC.
"I said the old joke, I have never worked here, Ma'am, I haven't worked for 40 years," he said.
He joked: "There was a long line of presenters and as she came in she first went over to Radio One, and I must say full marks to her for pretending to know who they were."
He added that the Queen was also shown a copy of the royal charter during her tour of Broadcasting House, the home of BBC radio.
Mr Humphrys, presenter of Radio Four's Today programme, said afterwards he had quizzed the Queen as to why Cuba's leader, who is also soon to be 80, was not among birthday guests at Buckingham Palace.
"I suggested it was a bit mean not to invite Fidel Castro to the Palace because he's 80 as well and she didn't seem to think it was a very good idea," he said.
Radio One breakfast presenter Chris Moyles said he had wished the Queen a happy birthday.
"She asked me what time I got up," he said. "And I said I was tired but it wasn't that early. I told her I listened to Wogan and John on the radio in bed and then get up. She said 'oh lovely'.
"She seemed sweet enough."
The Queen also officially re-opened part of the refurbished Broadcasting House.
During her BBC tour the monarch was shown other items symbolising the corporation's past and its future.
These included an ipod loaded with podcasts, digital radio technology, and a microphone her grandfather, King George V, used for his Christmas broadcasts.
Earlier on Thursday, the Queen visited the Royal Institute of International Affairs, one of the world's leading bodies for the analysis of international issues.
The Queen, who is patron of the organisation, heard a debate on the future of the world. The event was held behind closed doors.
After her visit, Baroness Williams, one of Chatham House's presidents, said: "The Queen has become much more relaxed in her 80th year - she has a lovely smile. Before she was quite shy".
"She's much more at ease, she smiles at people and relaxes with them. She's like a great oak tree - she's blossoming again."
The Queen will spend her birthday on Friday at Windsor Castle, where Prince Charles will host a family dinner.