LONDON (AP) — Britain is bracing for a four-day walkout by tens of thousands of doctors at the state-funded health care system that one official warned Monday could be “catastrophic” and postpone up to 350,000 appointments. A three-day doctors’ strike last month crippled the system that has been trying to dig out of an appointment backlog that predates the pandemic and has led to longer waiting times to see a doctor. Taylor, who said the strikes would risk patient safety, suggested the government and the union call in outside negotiators to help break the impasse