The mandatory sentence for murder is life imprisonment, as provided by section 2 of the Criminal Justice Act 1990. A sentence of life imprisonment means that the prisoner is subject to that sentence for the rest of his or her life. Such a prisoner has no right to be released early at any stage. If granted temporary release, the prisoner remains subject to the life sentence and can be recalled to prison at any stage.
Accordingly, the imposition of multiple life sentences, whether concurrently or consecutively, in a case where more than one murder is committed in the same incident, does not increase the severity of the sanction and has no such effect in practice or in law.