Depth of field: London project to dig vast underground cavern and cover with park

By Oliver Wainwright

A scruffy patch of former farm land in Hounslow is set to get the ‘mega-basement to end all mega-basements' as £50m-worth of gravel is excavated to create the UK's biggest subterranean space, with a new public park on top

While the billionaires of Kensington dig ever deeper to excavate multi-storey pleasure bunkers of private cinemas, swimming pools and car museums beneath their homes, there are plans afoot in an unlikely part of west London for the mega-basement to end all mega-basements. On a scruffy patch of land in suburban Hounslow a mile from Heathrow airport, surrounded by cosy crescents of semi-detached homes, planning permission has been granted to Formal Investments Ltd to dig out the biggest underground space in the UK. It will not be topped with an oligarch's mansion, but a brand new park for Londoners.

Driving along the busy dual carriageways that hem the site of Rectory Farm, you would have little idea that beneath this unremarkable stretch of former agricultural land, frequented by fly-tippers and the occasional travelling circus, lies a valuable bounty. Like much of the city's green belt, this 44-hectare (109 acres) swathe of land has been off-limits for years, being privately owned, too small to farm and protected from development. Yet beneath the topsoil lies £50-60m worth of gravel – an essential ingredient for the construction industry as an aggregate in concrete, which usually has to be trucked into the city from far-flung quarries or dredged from the North Sea.

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Source: Depth of field: London project to dig vast underground cavern and cover with park