23-year-old Gary Tweddle, originally from Reading, has gone missing in Australia's Blue Mountains.
He had been staying in Australia near Sydney for a work conference.
New South Wales Police say the search has now been wound down.
Gary's father David from Berkshire was helping searchers in Australia but says he still does not know what happened to his son.
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Most of the region's MPs will support the Government's motion calling for air strikes in Syria, writes Political Correspondent Phil Hornby.