Among a series of Lewis-base-stabilised antiaromatic dibenzoberylloles (DBBes) the cyclic alkyl(amino)carbene (CAAC) analogue undergoes a complex but highly selective thermal decomposition, involving the breaking and making of four bonds each, which yields a rare beryllium η2-alkene complex. Two-electron reduction of the CAAC-stabilised DBBe analogue yields an aromatic dianion.