The signing is by some distance the most controversial in British football for years and is certain to ignite the always simmering hostilities between supporters of the two north London clubs.
Announced shortly after noon today, the Campbell deal sparked tens of thousands of telephone calls and emails within minutes as the news spread around London.
Half an hour later there were already dozens of messages on Tottenham supporters' websites. Typical postings included: "He will never, ever be able to justify this. How on earth is he going to be able to face us again? How will he be able to face his friends from the club? He needs his head checking."
Tottenham fanzine editor Bernie Kingsley said: "I am sure there will be lots of anger when he comes back wearing the red shirt.
"Obviously I hope he falls flat on his face but I am sure he will do well. It's a shame he has not gone abroad."
Former Arsenal striker Alan Smith said: "It's a brave move but I think he'll do well there. The Arsenal fans will forget his connections, but for the Spurs fans to lose their main man to their arch rivals is a devastating blow - a real kick in the teeth."
Arsenal fans will now hope that the signing of Campbell will persuade their biggest star, French international Patrick Vieira, to stay. He has recently criticised the club's lack of ambition and, until today, appeared certain to seek a move.
In addition to Campbell, manager Arsène Wenger, who - unlike Tottenham's Glenn Hoddle - can lure players with the promise of Champions League qualification, has spent more than £20million signing Francis Jeffers, Giovanni van Bronckhorst and Richard Wright.
Within an hour of the announcement bookmaker William Hill cut Arsenal's odds on winning next year's Premiership from 11/2 to 5/1.