Most tennis players claim to treat every opponent the same and practice harder than they play.

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Most children are registered with a family doctor, but Fizza Qureshi, who runs Project London for Doctors of the World, a charity, says this is getting harder as practice managers insist on proof of status first.

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He talks about the NHS being a series of "microclimates" where good practice can exist alongside bad, making it harder to detect.

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Unfortunately, this practice is becoming increasingly common, and maybe we have to push back harder.

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In practice, though, the transactions tend to be more complex, and therefore harder to trace.

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