The 46-year-old singer-songwriter has reunited with his former Take That bandmate Robbie in London for a top-secret project that is set to create ''mayhem'' among fans of the pop group.
A source explained: ''Robbie is going to cause mayhem among Take That fans when his video is released.
''He shot it on Monday at a flat in Shoreditch in east London. It's for 'Mixed Signals', the song Brandon Flowers gave him. Gary was obviously more than happy to get involved with it.
''They talk all the time and have got all sorts of plans for new Take That stuff, but they knew this would be a way to whet our appetites.
''Robbie was filming all afternoon and drove in through a back entrance so no one would spot him.''
The video also features Robbie's actress wife Ayda Field and ought to be well received by long-time Take That fans.
The source told The Sun newspaper: ''Ayda came with him as she has a starring role in the video too.
''Gary came in the evening and filmed for a few hours. There's a clever idea behind it and all will become apparent soon. But it's safe to say that the fans will love it.''
The reunion is sure to ignite rumours of another Take That comeback for Robbie, who suggested in December that he was open to the idea.
Robbie said the band had no concrete plans in place, but admitted he'd like to make music with Take That again ''at some point''.
He shared: ''You can always fudge an anniversary of some sort. Like, it was the anniversary this year, but we got together in 1990, so the 25th anniversary would have been last year.
''Then there's the anniversary of the first song, the first anniversary of most people with brown eyes buying the record and so on.''
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