Most people would drop anything for the chance of a White House meeting with the President of the United States, but not David Attenborough.
The broadcaster and naturalist spent his 89th birthday with Barack Obama, and said it was a "great, great privilege" to visit the White House earlier this year.
But though he was impressed by the invitation, Attenborough wasn't about to cancel prior commitments to see him.
Attenborough meets Obama
After the pair's meeting was reported earlier this year, it has now emerged that just before the date, the President's office asked if Attenborough could alter the timings and visit 24 hours earlier than planned.
But having already promised to speak at Kew Gardens, Attenborough turned the president down, The Evening Standard reported.
"Attenborough was apologetic but firm," editor Sarah Sands wrote. "He had agreed to speak at Kew the night before. He fulfilled that engagement."
"A lesson for the over-invited," she added.
Luckily, the scheduling worked out and the meeting did take place in May. The White House released a video of the pair "discussing and contemplating the natural world" to prove it.
Watch David Attenborough's full interview with Barack Obama