Prof Sir Bruce Keogh said the proposals were about "improving outcomes" for patients.
It is about improving the outcomes for patients with very serious conditions - let me be absolutely clear, that two tier system already exists.
By serious conditions what I mean are trauma, heart attack, stroke, to name three of them.
– Professor Keogh speaking to BBC Breakfast
Ambulances already when they pick up somebody with major injuries take them to designated trauma centres, they already take people with heart attacks to specific designated heart attack centres and similarly for strokes.
We have shown that when you do that, that despite initial concerns that the additional travel time would create problems, that the outcomes for patients are significantly better.