MY eight-year-old son Charlie had been reluctant to go and watch his team, Manchester United, play at Leeds last weekend because the seats were in the rival Leeds' family stand. In the end, he begged me to go with him to provide some moral support and protection.

After a lifetime of avoiding football like the plague, this meant I had to become an undercover Manchester United fan, like Charlie, for the day - sitting beside his Leeds-supporting brothers while surrounded by about 35,000 other Leeds fans.

"You did say David Beckham had nice legs once, so you're sort of a Man U fan," he told me.

Charlie was wearing his lucky Man U underpants. In a gesture of solidarity, I wore a red top. "We'll be fine," I told him. "No one will know we're imposters."

As we waded through a sea of white-clad supporters to get to our seats, I soon realised why he had been worried. People jumped to their feet, chanting: "Stand up if you hate Man U, stand up if you hate Man U...."

This is sung, apparently, even when Man U, known as the Scum in Leeds, are not playing, rivalry between fans is so intense. We didn't stand. "Don't worry, I don't think anyone noticed, Charlie," I said unconvincingly.

Then, suddenly, everyone was up again, arms waving: "You're Leeds and we're proud of you, you're Leeds..." It was like being part of the chorus in a modern-day opera. At least the words were easy: "We all love Leeds, we all love Leeds..." And the tunes were simple enough.

All around us, grown men, who looked as if they could probably pass for normal adults outside the ground, were singing passionately: "Marching on together, we're going to see you win, tra-la-la-la-la-la..."

Behind us was football's answer to Pavarotti. A huge man, with a Scottish accent, he regularly burst into song: "Ref-ur-eee, ref-ur-eee..." waving his arms wildly, and, occasionally, clasping his head in his hands.

On the back of his football shirt was his name: Belly. Belly looked as if he would collapse with heart failure if he tried to kick a ball, but this didn't stop him giving a running commentary on where the players were going wrong.

The game, I confess, was exciting, not what I had expected. And the crowd's performance could be highly entertaining. When the other side missed a goal, everyone stretched arms, pretending to be aeroplanes. When Man U scored, Leeds fans were deathly silent. By the time Leeds were losing four to one, Belly's voice rose a few octaves. Veins were throbbing on his forehead.

After much more excitement, the final score was 4-3 to Man U. Belly was downcast. As we moved with the crowd, I was thinking football wasn't so bad after all, but it was time to console my other boys, the two Leeds fans. "It was a fair result, the better team probably won. But Leeds sparkled in the second half. They'll do better next time," I said.

As someone merely masquerading as a football supporter, I was soon put in my place: "Mum, stop sounding so balanced and even-handed. That is not the way to behave at a football match..."

"You don't think I fooled anyone then?"