From "Tinker Tailor Soldier Spy: Tinker Tailor (#1.5)"
Can I have a brief, please? Control, I need a brief! We must say something! Do you want me to deny it, a flat denial just to start with? Do you want me to get someone else? Do you want to come downstairs and handle it yourself?
It's deniable. He had foreign documents. No one could know he was British at this stage, even if he's not dead.