Even now, central London has a surprising variety of hidden pockets of open ground. The greenest are disused burial grounds, far away from the parish church in question, closed in the mid 19th century and later handed back to Londoners as public gardens. They offered (and still offer) what Octavia Hill, housing reformer and open space campaigner, called “open air sitting rooms”. Equally hidden are the old routes, passages and working mews that pepper Clerkenwell, Holborn and Fitzrovia.

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