"...
1.) Overview—Right of Abode:
Having the Right of Abode means you’re allowed to Live or Work in the UK Without any immigration Restrictions.
If you have the Right of Abode, you do Not need a Visa or Electronic Travel Authorisation (ETA) to come to the UK.
There’s No Limit on the Length of Time you can spend in the country.
Who has the Right of Abode?
All British Citizens automatically have the Right of Abode in the UK.
Some Commonwealth Citizens may also have the Right of Abode.
How to Prove you have the Right of Abode?
You can Prove you have the Right of Abode if you have a UK Passport describing you as a British Citizen or British Subject with the Right of Abode.
Otherwise you need to apply for a ‘Certificate of Entitlement’.
...."
"...
If you have a Valid British Passport:
You Cannot have a Certificate of Entitlement at the same time as a Valid British Passport.
...."
>
***************************************