Complex sentence: In January 1969, Odhams ceased to exist as a publishing imprint and "Smash" became an IPC Magazines publication, although most of the consequences of this change didn't become apparent until the March 15th issue, in which the comic changed drastically.
Split into simpler sentences: In January 1969 Odhams ceased to exist as a publishing imprint, and "Smash" became an IPC Magazines publication. Most of the consequences of this change didn't become apparent until the March 15th issue, in which the comic changed drastically.