The UK’s hallowed National Health Service (NHS) turns 70 this week, and Prime Minister Theresa May has said that she will be giving it a special birthday present: an extra £20 billion in England per year by 2023. As a result, NHS funding in other parts of the UK will rise too. She wants the £20 billion to “secure the future” of the service while delivering “world-class” care. But she risks failing to achieve either aim.

For starters, …