You can still feed the birds in Trafalgar Square (for £50 a bag)

Eye witness: Pigeon wars - From tomorrow, a long-standing London tradition will become a punishable offence.

Where have all the pigeons gone? Frightened or starved away, so tourists can sit in the freezing London wind and drink preposterously priced lattes from paper cups. There used to be 4,000 pigeons in Trafalgar Square, and when we were children many of us would buy feed from the man with a stall - he was there for 50 years - and hold it out until they fluttered and cooed and pecked on our arms and shoulders and heads and we laughed and someone took a picture. It was great. But it was unhygienic and didn't fit in with modern London so it had to stop, said the Mayor, Ken Livingstone. So from tomorrow, anyone caught slipping a crust to the few remaining feral birds under Nelson's gaze will be fined £50.

There are already signs - in six languages - around the square saying "Do not feed the pigeons". The byelaw does not come into effect until tomorrow, but the intimidation works. June Adams has come down from Edinburgh for the weekend, and at breakfast in her hotel she wrapped a bread roll to give to the pigeons. Which is what she was doing until one of the Mayor's new Heritage Wardens in a fluorescent jerkin came and asked her to stop.

"Last time we were here it was with the children and the whole family was feeding the birds," she says, still blushing with embarrassment. "I didn't know you were not supposed to now. He was very polite but firm, you know?"

Her husband chuckles. "So Ken has had a hit with the congestion charge. What's this - an indigestion charge?"

Attitudes at the café tucked into a corner of the square are not quite as facetious, though. Visitor numbers to the square are up 350 per cent - 760 people walk across it every hour. It is cleaner, quieter, more like Sir Charles Barry intended when he laid it out in 1840, long before our wasteful ways with food and packaging made the place a permanent pigeon party.

"It was filthy here before, and sticky," says Prudence from Leatherhead, talking to her friend at one of the tables outside the café. Two coffees, a biscuit and a ham sandwich have cost her more than £8. "The pigeons made a mess of everything. You couldn't sit here like this. Who would want to?"

"The kids used to get covered in pigeons and so on," says her friend Angela. "Heaven only knows what it did to them."

The pigeons were a public health risk, said the Greater London Authority's biodiversity manager.

Campaigners disagreed and claimed it would be cruel to "starve" the birds out, so a compromise was reached which meant feeding the pigeons less and less over time. A company was also hired to bring in a hawk every day.

The pigeons vanish moments before any humans in the square notice the predator looking down from the head of General Napier. It flops into space and opens big lazy wings to glide down over the heads of tourists and perch on a Landseer lion.

The hawk man is chatting to a foreign television crew, holding up his gloved hand behind the camera so the bird comes swooping low over the lens. "He's flying around eight hours a day so he is working more than he would in the wild," says the hawker, employed by a company called Van Vynck Avian Solutions.

The company's website is particularly piquant to those who will rally in the square this week to protest against George Bush. The bird of prey whose ominous wings and cruel beak bully the flocks of Trafalgar Square is a Harris Hawk, a species introduced to this country "from the United States". The message to the pigeons is clear: any too stupid to realise what's good for them and embrace the benefits of freedom will be terrorised. No parallels there, then.