In a mystery worthy of Edinburgh's fictional police detective Rebus himself, audiences at the Scottish capital's book festival on Saturday were left guessing over the identity of the "man of big brain and good heart" about to be interviewed by crime writer Ian Rankin.
Puzzlement turned to delight when the mystery guest turned out to be Prime Minister Gordon Brown, currently enjoying his summer holiday.
Appearing at the opening of the 16-day literary event, the British premier looked relaxed as he faced the questions of Rebus's creator – said to be his favourite author - in front of an audience of 500.
Mr Brown's own work – he has penned several non-fiction books as well as contributing a story to the just published children's charity book Wow! 366 - came up for praise from his best-selling interviewer, who said he thought the Prime Minister's writing style was great.
"I've been learning from your novels," admitted Mr Brown.