Though primary care groups may be based on 'natural communities', they are not natural organisations, Sir Duncan says.

'They have no infrastructure to work with. There are lots of examples of in-fighting. There's no tradition of hierarchy, even in the softest sense of the word. There's no explicit culture of addressing under-performance collectively in practices or individuals - and you don't grow these things overnight.

'Those are all major development problems. Don't let's expect it to be easy. If it's rocky in the first few months or years, let's keep persevering. All those things are going to make PCGs very difficult organisational creatures.'