Blair drops in on the ultimate networking party

SUN VALLEY, IDAHO (Fortune) -- Tony Blair, who barely two weeks ago handed over the reigns of power as Britain's prime minister to Gordon Brown, is planning a surprise visit to Allen & Co.'s annual media mogulfest at this mountain playground later in the week, Fortune has learned.

The visit has not been announced, and the details have been kept hush-hush for obvious security reasons. But he is expected to speak here either Friday or Saturday - even the high-profile guests have not been told for sure which day he will arrive. Blair's visit will add even more star power to this already high-wattage event, which annually brings together the highest-profile names in media and technology for several days of dealmaking and recreation.

Former prime minister Tony Blair

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In recent years other powerful politicos have attended - including the prime ministers of Canada and Turkey - but none with the stature of Blair. While his visit may come as a surprise, Blair has had a long relationship with one of the conference's highest profile attendees: Rupert Murdoch.

Murdoch, who arrived here Tuesday, is one of the most closely-watched guests, as his attendance comes smack in the middle of his attempted $5 billion takeover of Dow Jones (Charts), the parent company of The Wall Street Journal (Allen & Co. itself is advising News Corp. (Charts, Fortune 500) on the deal). Murdoch often visited Blair at 10 Downing Street, and published reports have speculated the media titan may offer Blair a seat on News Corp.'s board of directors.

Allen & Co., the New York investment bank that caters to the media and technology industries, began holding the conference 25 years ago, and it quickly became a can't-miss summer event for CEOs and money managers lucky enough to get an invite. Officially, the event is closed to the press - which has only added to the event's luster by giving it a veneer of secrecy. In truth, journalists lurk in the shadows here every year.

The lush grounds of the resort and golf course have often served as the breeding grounds for deals. In the 1990s, Disney's (Charts, Fortune 500) acquisition of ABC/Cap Cities was largely negotiated here. Last year, YouTube CEO Chad Hurley was the big star, and months after the conference sold the Web video company to Google (Charts, Fortune 500) for $1.6 billion.

Among the bold-faced business names either already here or slated to arrive are: Bill Gates; recently-deposed Yahoo! (Charts, Fortune 500) CEO Terry Semel; former Disney chief Michael Eisner; Paramount Pictures CEO Brad Grey; movie mogul Harvey Weinstein; and former Viacom (Charts) CEO Tom Freston.