Same thing happened to me this weekend - we were 100 miles from home on a day trip, changing our daughter's nappy (diaper!) in the trunk and my wife put the keys down in the trunk after having opened the trunk only (rest of the doors stayed locked). Then, just as I was trying to open the rear door to put my daughter in the car seat, my wife slammed (why do women always do that! ) the trunk shut and, just as she did, we both looked at each other, time stood still, and we knew what she'd done! Car locked, keys inside! Fortunately BMW assist came in 30 minutes and opened the trunk in less than 10 minutes using the method Mindfull describes above. The alarm (which was pretty pathetic) went off and then he was in......makes you think twice about ever leaving anything in the trunk for too long. If it had been the AA or the RAC I am sure they would have smashed the window to get in.

Will be getting BMW assist again when the warranty expires!!