This from the TfL site....

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Current Overground network status
A good service is operating on all London Overground lines.

Other London rail operators
ONE RAILWAY: Due to a late finish to engineering works One services are not
serving Liverpool Street station.
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To me this seems like a contradiction. The problem is that the Liverpool
Street line is a London overground line, but it isn't a London Overground
line. TfL should not have used "London Overground" to mean a small subset of
what the words have meant for the last hundred years.