Focus Ghia X 55 plate Central Locking question

[heisthegaffer]

Dear all

A friend of mine has a 55 plate Focus Ghia x and managed to lock her son and keys in it recently and had to smash a window to get them both out.

She says that she unlocked the car, put her son in (and keys by mistake) and shut the door. The car then locked itself a few mins after.

Is this normal? My old 182 had a feature which locked the doors after a few mins if you'd unlocked but not opened a door, but for a car to lock it's doors after a door has been opened just doesn't sound right to me.

Anyone know if there is a way of disabling this feature if it part of the design?

Thanks all