The makers of Die Hard have just explained a big plot hole in the middle of the movie, and it's only taken them three decades to give us the truth.

To jog your memory in case you've forgotten, baddie Hans Gruber (Alan Rickman) pretends to be a hostage when he first comes face to face with John McClane (Bruce Willis).

McClane suspects that something is off and manages to get away - but it is never specified what exactly set off his alarm bells.

Screenwriter Steven E de Souza has now explained, at a 30th-anniversary screening of The Running Man, that we're missing a helpful scene about the synchronised watches of the terrorists that was cut out in the final edit.

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"Originally, they get off the truck, the camera craned up, you saw them in a circle and Alan Rickman says, 'Synchronise your watches'," de Souza explained (via Slash Film).

"They all put their arms out in a circle with the camera moving down and they all had the same Tag Heuer watch. If you notice, the first guy Bruce kills almost by accident going down the steps, he searches the body, looks at the IDs."

Also in a longer cut of the scene, McClane begins to notice the terrorists' watches, de Souza adding: "He steals the cigarettes, which is a laugh.

"He looks at the watch which gets another laugh because you're thinking he might steal the watch. As he kills each guy, he notices they all had the same watch.

"When he talks to Dwayne Robinson, he says, 'I think these guys are professionals. Their IDs are too good. There's no labels on their clothes and they all have the same watch'."

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Bear Grylls//Digital Spy

However, the "synchronise your watches" bit was cut in the end because it came into conflict with the plan for the terrorists to escape in an ambulance, which was added towards the end of shooting.

Argyle (De'voreaux White) the limo driver crashes into the escape ambulance, but that ambulance was absent in the "synchronise" shot, thus leaving an even bigger potential gap.

De Souza added: "[Director] John [McTiernan] says to the editor, 'Get the scissors in there. Cut as soon as you can when they get off the truck so we don't see there's no ambulance'. Now without 'synchronize your watches', all of these moments where Bruce looks at these guys' watches makes no sense.

"When Bruce offers the cigarette to Alan Rickman, Bruce sees the watch. You see his eyes look at the watch. That's how he knows that he is one of the terrorists."

From: Digital Spy