Jimmy Smith headed Orient into a shock lead at the Liberty Stadium after the visitors were bombarded by Swansea for the entire half.

Smith repeated the trick he pulled at Norwich during the previous round by getting his head on the ball inside the area to turn the tie on its head.

Daniels supplied the cross from out wide and Smith beat keeper Ma-Kalambay to the ball.

But it did not last until half time as Van Der Gun’s nodded header on 45 minutes levelled proceedings.

Orient’s goal came totally against the run of play. Swansea dominated proceedings for the whole half, but the hosts could not break through the determined O’s line until the end of the first 45 minutes.

Orient nearly went into the break 2-1 down, but Pratley was ruled offside on the goal-line when he accidently deflected a shot into the net.

The O’s were up against it from the early stages as Swansea came out on the front foot in this FA Cup tie.

Ben Chorley blocked Van Der Gun’s strike on three minutes after a through pass sliced through the back line and caught out Charlie Daniels.

Chances to build up attacks were non-existent for Orient as the game was played in their own half during the opening exchanges.

With the hosts pressing high up the pitch, Dean Cox moved from the wing into the centre of the park in search of action but could not impose his passing game on proceedings.

The midfield was ruled by Swansea as Orient struggled to get a foothold in the game.

Keeper Jamie Jones saved well at the post from Scott Sinclair’s long range effort on 17 minutes.

The first sniff of goal for Orient came on 23 minutes when McGleish headed over from a off-side position after Dean Cox somehow won a header in the box from Charlie Daniels’ free kick.

Sinclair blazed over on 29 minutes from the 18 yard line after turning Whing inside out.

The hosts put up a wall at the other end and blocked out Cox and McGleish when Daniels' crosses did get the ball into the danger-zone at set-pieces.

But set-pieces were the sole outlet for Orient and Daniels’ passing posed the biggest and the only real threat.

The task during the second half will to win the battle in the midfield against rampant Swansea.