6. A combined speech recognition and voice authentication method, comprising: responsive to a user being successfully authenticated by a voice authentication function, accessing a personalised set of acoustic language models for use by a speech recognition function in recognising one or more utterances by the user, the acoustic model set containing acoustic language models which have been trained using voice data derived from utterances provided by the user either during enrolment with the authentication function or during one or more subsequent authentications.
6. A combined speech recognition and voice authentication method, comprising: responsive to a user being successfully authenticated by a voice authentication function, accessing a personalised set of acoustic language models for use by a speech recognition function in recognising one or more utterances by the user, the acoustic model set containing acoustic language models which have been trained using voice data derived from utterances provided by the user either during enrolment with the authentication function or during one or more subsequent authentications. 7. A method in accordance with claim 6 , wherein the personalised model set comprises acoustic models of speech units which have been trained utilising speech samples provided by one or more other users having a shared voice profile to the user.