Hugh

I would suggest that you appear to be conflating barristers (not lawyers) chambers, and "immigration barristers chambers" - whilst quite a few chambers have renowned immigration law practices, they are almost always multi-disciplinary, providing advocacy in many other areas.

For example
Goldsmith Chambers
Animal Rights
Civil
Clinical Negligence & Healthcare
Crime
Extradition
Family
Immigration and Public Law
Inquests and Inquiries

Doughty Law
Actions Against the Police and Public Authorities
Administrative & Public Law
Anti-Trafficking, Modern Slavery and Business & Human Rights
Business Crime & Investigations
Children's Rights Group
Climate and Environmental Justice
Clinical Negligence, Personal Injury & Product Liability
Community Care and Health
Court of Protection & Mental Health
Criminal Law
Criminal Appeals
Education
Employment, Discrimination and Equality Law
Extradition
Housing, Social Welfare and Property
Immigration
International Law
Inquests and Public Inquiries
Media, Communications & Information
Mediation
Professional Discipline and Regulation[/quote]

Any KCs from any chambers who have been made Judges (when they have to leave the Chambers) could actually have been specialising in one of many areas of expertise.

I put it to you that unless you can provide a solid evidentiary link between Judges who previously specialised in Immigration Law in a multi-disciplinary Chambers, and before becoming Judges had advocated on behalf of clients and the clients’ solicitors on Immigration matters, and then subsequently, after becoming a Judge, have ruled in favour of Barristers from the Judge’s previous Chambers on an Immigration matter, your rhetorical question

is more imaginary than hypothetical…