From the outside, have an assistant (e.g. wife) hold the open handle.

From the inside, try inserting a small instrument screwdriver (*NOT* a jeweler's screwdriver, that will break) between the holding bar, and the claw in the lock mechanism. It engages from the passenger side of the car (left side from inside the trunk), if I am not mistaken.

You may need to remove the inner lining of the trunk (turn the little gray ovals with a large flat blade screwdriver), and try to remove the latch mechanism. Remember you'll not only need to remove the securing bolts, but the lock and handle links as well.

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