If you need to give a British colleague critical feedback, do it privately. Criticism delivered in front of others—in meetings, in open offices, copied on emails—is experienced as humiliation, regardless of whether the criticism is accurate. You may be right, but you’ve also caused harm by making their failure visible to witnesses.
This matters because face is relational—people’s standing exists in the eyes of others. Private criticism can be absorbed and addressed. Public criticism damages standing in ways that are hard to repair. Even if someone has genuinely failed, calling them out publicly adds humiliation to failure.
Some contexts license public evaluation—formal reviews, published work, institutional assessment—but these have special conventions. In normal professional interactions, keep critical feedback private.