Apple has reinstated the ability to "Enable 3G" in the iOS 5.1 update it rolled out this week.

The feature, which was removed in iOS 5.0.0 and iOS 5.0.1, means that users can now turn off 3G on their iPhone if they want to try to conserve battery life if they are running low or aren't surfing the web when out and about. 

"Using 3G loads data faster, but may decrease battery life," warns Apple underneath the new setting. 

Apple released the iOS 5.1 update on Wednesday for all iPhone, iPad, and iPod touch users.

The new update - which is available either via the Software Update feature within iOS or by connecting your Apple device to your computer and iTunes - brings several other new features, including a camera shortcut which is now always visible on Lock Screen for iPhone 4S, iPhone 4, iPhone 3GS, and iPod touch (4th Generation) and camera face detection now highlights all detected faces.

It also fixes bugs that were affecting battery life.

You can get the download now.

Thanks to David Fanning and David West for the screenshots