The King's Fund's response to the consultation on reforming London's healthcare following Lord Darzi's landmark report is a scene-setter for the debate that will follow the publication of his national strategy in July.

One of the major tensions Lord Darzi faces in his next stage review is how to fashion a national strategy for a health system where the dynamic is towards local decision making and competition.

Clues on the most appropriate way forward come in the measured verdict of the King's Fund on his London work. The think tank agrees there is compelling evidence on the need to deliver better specialist services on fewer sites for those who have been struck by trauma, stroke and some other conditions. It urges decisive action, implying that public opinion urging the contrary must not divert policy makers.

But it advises caution over changes for which, it believes, the evidence is weaker, notably polyclinics. It argues there is no overriding case for GPs to be moved en masse into larger teams, and highlights the adverse impact of increasing travelling distances for some patients.

The think tank's response to the London consultation makes clear that, while there are absolutes to be divined about stroke and trauma services, each primary care decision needs to be made on its own, local merits.

Over the final three months of the Darzi review the Department of Health needs to manage expectations about what it can and cannot deliver. The work the health minister has initiated is vast; hundreds of people are involved. But he cannot hope to produce a detailed plan for every part of the NHS, and neither should he.

A win for Lord Darzi would be to define, celebrate and propagate the values of the NHS, building a consensus on the rights and responsibilities of staff and citizens. He should set out a clear national plan for services that are crying out for one, such as trauma, lay out effective clinical pathways and drive home messages on safety, access and choice. When it comes to the options for reform on issues such as primary care structure, he must give local services the freedom and encouragement to innovate, lead and shape.