A branch target buffer, BTB, is provided to store at least one BTB entry corresponding to a respective branch in a control flow in a sequence of machine-readable instructions of a computer program. The BTB has a tag field to compare with a program counter of a fetch address generator and at least one further field to store information characteristic of the branch instruction identified by the corresponding tag field and allowing a conditional branch to be distinguished from an unconditional branch instruction. The BTB has a predetermined storage capacity and is utilized such that unconditional branch instructions are preferentially allocated storage space in the BTB relative to conditional branch instructions.