Gov.uk says the following, which seems to apply;
RIGHT OF ABODE IN THE UNITED KINDOM – NOTE FOR BRITISH CITIZENS
All British Citizens have the right of abode in the United Kingdom. If, as a British Citizen, you wish to travel on a non-British passport it must be endorsed to show that you have the right of abode. Otherwise, you might experience difficulty proving your right to be re-admitted to the United Kingdom.
Certificates of entitlement to the right of abode are issued by the Home Office to applicants to the United Kingdom and by the appropriate British representative to applicants abroad. A fee is payable in both cases. Certificates can only be issued to someone who does not have a British passport or identity card describing them as a British citizen or British subject with right of abode. A certificate will cease to be valid once the passport it is attached to expires and cannot be transferred from one passport to another.