However, after only 8 minutes Sol Campbell tapped a harmless back-pass towards his own goalkeeper and as Lehmann made room to clear the ball he struck the advancing Viduka on his boot and the ball flew into the net.
Too good to be true? Unfortunately yes.
It took until the 26th minute for Arsenal to level when a fluent move involving Patrick Vieira and Kanu found Freddie Ljungberg whose cross was crisply volleyed home by Henry.
Seven minutes later, Henry sent over a perfectly judged ball that Edu's sliding lunge drove in.
This was the 42nd FA Cup tie Arsenal have played under Arsène Wenger and outside finals and semi-finals, they have lost only one without the aid of a penalties. That was against Leeds in January 1997.
They scored two more goals of quality, the first when Henry held the ball up long enough to send sub Robert Pires through.
Then, in injury time, Henry found Pires in the box again and the winger stroked the ball back across the box for another sub, Kolo Toure, to prod home easily.
Leeds United (4-5-1): Robinson; Richardson, Duberry, Kilgallon, Harte; Smith, Bakke (Sakho, 70), Batty, Matteo Milner (Lennon, 84); Viduka.
Substitutes not used: Carson (gk), Johnson, Olembe.
Arsenal (4-4-2): Lehmann; Lauren, Campbell, Keown, Cole; Ljungberg (Pires, 80), Gilberto Silva, Vieira, Edu (Parlour 80); Kanu (Touré 80), Henry.
Substitutes not used: Shaaban (gk), Bentley.
Referee: R Styles (Hampshire).