How can I downgrade from 1.1.3 to an earlier version of iPhone firmware?

For some time it was thought, and reported many places (here included), that there was no downgrade from 1.1.3 once you had upgraded. This was due to the fact that 1.1.3 upgrades the iPhone baseband, and that downgrading to an earlier firmware would leave the new baseband intact and the resulting iPhone firmware incompatible with the baseband.

Thanks to the efforts of the iPhone development community, this is no longer the case. If you would like to downgrade your iPhone 1.1.3, follow these downgrade instructions.

This has recently become of particular importance due to the newly released iPhone 1.1.3 jailbreak which requires 1.1.1 or 1.1.2 firmware present on the iPhone.

We have not tested these methods, but many of our readers have told us of their success using this method.