In … 2013, a high court judge struck out Belhadj’s case against the British government, on the grounds that if it were allowed to proceed it could potentially damage British national interests. At [a] Tribunal in January 2014, his lawyers said they had reason to suspect that GCHQ had been intercepting their phone calls with Libya-based Belhadj, and noted: “The right to confidential client-lawyer communication is a fundamental principle of justice.” This later turned out to be the case, and but one case of many.

https://en.wikipedia.org/wiki/Abdelhakim_Belhaj?wprov=sfla1