The young striker extended his fine form in cup competitions this term with his fourth goal in five cup ties to fire us into the lead in the first half.
Both goalkeepers were on top after that as Tolga Zengin denied Harry twice and at the other end, Hugo Lloris was in unbeatable form with four first-class saves to keep the Turkish side at bay.
It looked like we were going to hold on for maximum points only for a late handball to deny us as Demba Ba slotted home from the spot in the 89th minute.
“It was great to get on the scoresheet again but we’ve come away disappointed,” reflected Harry.
“We dug deep as a team and to concede so late is heartbreaking on our behalf.
“Besiktas are a top side, they were unucky not to qualify for the Champions League so we knew we’d have to be at our best.
“They created a few chances but Hugo is a top goalkeeper and pulled off some world-class saves.
“It would have been a great win and we really wanted to win this game, we knew it would be a big game in the group. We had chances as well, their goalkeeper made a couple of good saves, but we have to move on.”
Below: A graphic of Harry's goal - more stats and reaction on our Match Centre...