An inkjet printer comprising a printer body and a replaceable printhead cartridge is disclosed. The printhead cartridge has a casing that supports a printhead and a plurality of contacts for receiving print data and power. The printer body has a cradle for holding the printhead cartridge in an operative position. The printer body has corresponding contacts for connection with the plurality of contacts on the printhead cartridge when the printhead cartridge is in the operative position. During insertion of the replaceable printhead cartridge, the casing is first slid into the cradle at which point the plurality of contacts contact the corresponding contacts. Next, the casing is rotated. During the rotation the plurality of contacts remain in contact with the corresponding contacts. The rotation of the casing in the cradle forms an over centre mechanism.