Scott Brown's smile could not have disappeared any quicker.
The Celtic captain fell victim to a prank by a couple of brave Rangers supporters recently and it's safe to say that Brown did not see the funny side of it.
Brown is accustomed to requests for autographs and photographs from hardcore Hoops fans and he happily agreed to stand between two young men who asked for a picture while the Scotland international walked through an airport.
The 32-year-old smiled kindly as he put his arms around the pair, who promptly broke into Rangers' famous chant: "We are the people."
https://twitter.com/sportingawayday/status/885591072453296129?ref_src=twsrc%5Etfw&ref_url=http%3A%2F%2Fwww.talkingbaws.com%2F2017%2F07%2Fvideo-scott-brown-gets-pranked-rangers-fans-shouting-people%2F
Brown's mood understandably changed very quickly because he's Celtic through and through and he exited the scene sharpish, shoving one of the fans away lightly in the process.
Last month, a Rangers supporter pulled the exact same prank on Brown, who may think twice before posing for photographs with fans who aren't sporting Celtic gear.
The Bhoys skipper bleeds green and white and, as such, he does not see eye to eye with those who have an affinity for their Old Firm rivals.
One look at his famous celebration in El-Hadji Diouf's face tells you everything you need to know about how much it means to him to get one over on his club's noisy neighbours.
https://www.youtube.com/watch?v=VCYU9V-MXE0
