My heart is racing and I've lost control: I've just become a victim of Pitt-mania

Forget the impact of the Beatles, the anarchy of the England riots or even just the carnage of Buchanan Street on Christmas Eve - Pitt-mania has hit the streets of Glasgow.

Men, women and children surround the newly transformed George Square, peering round the yellow stop signs, falafel carts and other features of the all-American mise en scne. The crowd expands throughout the morning as the public eagerly await a glimpse of the star.

"It's our boy's first day at school, so I thought we'd come see Brad before picking him up," says Kenneth Bradford, a worker at Langside College. He and wife Trisha plan to spend hours at the filming location for World War Z, in the hope of seeing the 47-year-old.

Maggie Buchanan, 25, a retail manager from Gourock, also admits to being an avid fan of Pitt. "I've been here since 9am and I'll stay here until my last train if I have to!"

I perch on a railing used to cordon off the Glasgow streets, yet fail to find any enthusiasm within me. I mean, it's Brad Pitt, the king of action, exposing his talents (and perfectly carved abs, ladies) in such iconic roles as smooth-talking Rusty Ryan in Ocean's Eleven and the violent Irishman in Snatch. I should be more psyched.

"He's the boss. Definitely the guy to be," said 19-year-old Gavin Grant, who had made the trip with a friend to join the hype. "If I saw him, I would probably just say I want to be like you. What should I do?"

It reaches midday with little activity, except for the movement of two rain shelters during a downpour. The crowd acts oblivious to the elements and boycotts any notion of taking refuge under the nearest building. Instead, cameras continue to ferociously click away. I hear a range of accents - Scottish, English, European, even a group of Asians - all congregating here for Brad. The more I analyse my surroundings, the more ludicrous it becomes. Here I am, waiting in the rain, for a forty-something married man. I may be going crazy.

One particularly enthusiastic fan, 45-year-old Sharon Outhwaite, has stood in the same spot since 7:30am for three consecutive days. Today she admits skipping lunch, just for a mere peak of the "god-on-legs". Her commitment is impressive, if a little frightening.

I give up on the pitiful weather and enter a quiet pub on John Street. To my surprise, a devilishly handsome Brad Pitt suddenly passes my window. Staff and customers shriek in unison. There he is, dressed in midnight blue, sexily pushing his surfer-style hair through his fingers. Thirty minutes later, he is back to please a whole new audience in the pub. I thrust myself into the booth of a family trying to enjoy a late lunch for the optimum stalking view. I want to shout, knock, act psychotic, anything to grab his attention. He moves out of sight and I feel disheartened. I missed my chance.

My heart is literally racing with adrenaline. I've lost control. My diagnosis? I am, without a doubt, the latest victim of Pitt-mania - and it's here in Glasgow to stay. Well, for 17 more days at least.