Tottenham have been thoroughly schooled tonight. After making seven changes against a side who are still within touching distance of Bayern Munich, Mauricio Pochettino was asking for trouble. He got it, with Borussia Dortmund tearing through his side with ease. The return leg follows at White Hart Lane next week, but you feel this one is already over.
FULL TIME: Borussia Dortmund 3-0 Tottenham Hotspur
Three minutes of added time remain.
Tottenham come forward again, looking for something to take back to north London but it comes to nothing as Trippier lifts a woeful ball in from the right that sails over the bar and out of play.
That's enough from Reus and Aubameyang tonight, they are off to be replaced by Kagawa and Ramos for the last few minutes.
That Onomah incident took place just outside the box but it did look like he was tripped by Hummels.
Tottenham have what looked to be a very decent penalty shout turned down as Onomah burst into the penalty area, but the referee didn't even consider it as he waved play on.
Dortmund and throwing attack after attack forward now. Again Castro wanders into acres of space down the inside left and tries to ping a cross in, but this time Wimmer stops it.
Tottenham and Mauricio Pochettino have been taught a real lesson here tonight. Yes, they are in the thick of a title challenge, but making seven changes for a clash against a team of this quality was only going to end one way.
Time for Kane. He's onto replace Son for the final 15 minutes of this match.
Dortmund nearly have a fourth after another wonderful passage of slick passing. Schmelzer is eventually picked out cutting in from the left and lifts the ball into the six yard area where Mkhitaryan runs onto the ball, but he lashes his effort wildly over the bar.
Son has what is probably Tottenham's best opening of the match in front of him, but can't get a decent shot off and instead rolls a tame one straight at the Dortmund goalkeeper.
Dortmund have a third and its a truly sublime goal. Aubameyang jinks past one challenge before sliding a ball out to Castro on the inside right. He clips a wonderful first time ball into the six yard area, threading it in between Wimmer and Alderweireld right onto the outstretched boot of Reus who thrashes it past Lloris. Excellent stuff.
Goal! Borussia Dortmund 3-0 Tottenham Hotspur (Marco Reus, 69)
Lamela picks up a yellow card moments after coming on for a late challenge on Wiegl.
Another change for Spurs, but still no Kane. Erik Lamela now enters the fray, replacing Eriksen.
Hummels nuts a cross from Son clear and Tottenham have a corner. Still no sign of Harry Kane, with the South Korea international now playing up front.
The introduction of Subotic was Tottenham's undoing there, no one really picked him up as he steamed into the box.
Dortmund have a second! From a short corner, Castro swings in a delightful ball what Subotic, just off the bench, meets with a firm header, knocking it over to the far post where Reus has slipped off his man to lash into the roof of the net. It was coming, and Tottenham are now in danger of letting this tie slip away from them.
Goal! Borussia Dortmund 2-0 Tottenham (Marco Reus, 59)
Also a change for Dortmund as Neven Subotic trots on for Bender.
A change for Tottenham sees Mousa Dembele brought on for Chadli.
Huge chance for a second for Dortmund as Mkhitaryan frees Aubameyang, who clips the ball over the onrushing Lloris. His effort is going wide but Castro can get on the end of it. He tries to clip it back on goal from an impossible angle and is denied by the outside of the post.
If you are just joining us, Squawka's heat mat from the first half should sum up how the first 45 went for you...