London's Top 10 Deepest Holes

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By M@ Last edited 16 months ago
London's Top 10 Deepest Holes
View looking up from the bottom of a huge hole. It's been artificially tweaked to look violet for some reason.

What's London's biggest hole?

If, with a cynical sneer on your face, you answered "Willesden", then you're unexpectedly right.

Willesden was the site of London's deepest ever borehole. In 1948, D’Arcy Exploration Co. Ltd dug a staggering 817 metres down through the capital's strata. That's more than 14 times deeper than Hampstead tube station.

They were prospecting for oil, believe it or not. An earlier borehole in Willesden had detected promising traces of the black stuff. D'Arcy and Co came in to do the follow up on Gibbons Road Recreation Ground (you may be able to see its footprint in satellite view). The fact that, today, we don't talk about the Willesden Oil Rush tells you all you need to know about their results.

The story of the Willesden hole has been told in some detail by A London Inheritance blog. As its author notes, "The borehole was capped, and concrete was used to fill the hole from a depth of 1,000 feet to the surface – strange to think that this long concrete column now sits below Gibbons Road Recreation Ground – for comparison, roughly the same height as the Shard".

But it's by no means the only big dig in town.

London's top 10 deepest holes

A map of central London with hundreds of dots showing borehole locations
Every red dot on this map is a borehole deeper than 100 metres. Via the BGS's database.

The British Geological Survey's map tools are a wonder to explore. Among various layers, such as chalk deposits, glacier boundaries and local gravity readings, you can also visualise every borehole recorded in London.

There are thousands, if not tens of thousands. Have a play and discover your own nearest borehole (though, bear in mind it's probably been filled in, and you can't drop a coin and make a wish).

The data (here rounded to the nearest metre) can be ranked to find the deepest holes ever dug in London. Willesden turns out to be Boring Central...

  • 817m: Willesden (1948)
  • 617m: Beckton Sewage Treatment Works (2006)
  • 610m:  Stonebridge Park Laundry, Willesden (1911)
  • 440m: Richmond Waterworks (1876)
  • 404m: Thamesmead Heatflow (1984)
  • 398m: St Helier Hospital, Carshalton (1939)
  • 397m: Kentish Town waterworks (1856)
  • 396m: Griffin Brewery, Chiswick (1912)
  • 388m: Streatham Common (1888)
  • 376m: Otto Mønsted Margarine, Southall (1910)

You'll note that many of these were dug out over a century ago. Back then, the aim was usually to secure ground water for waterworks, brewing, laundry facilities and other intensely aquatic pursuits.

The deepest in central London was that dug in 1843 at the Meux Brewery on Tottenham Court Road (site of the famous beer flood, and now the Dominion Theatre). That reached 349 metres, which is staggering when you consider how long ago this was.

Deep though these shafts are, they're pinpricks compared to the world's deepest holes. The Kola Superdeep Borehole in Russia goes down 12,262 metres (7.6 miles), possibly deep enough to disturb balrogs. The UK's deepest is 2.8 miles, in Cornwall.

Top image is the view looking up from London's deepest tunnel — the Lea sewer — which the author visited in 2015. At 75 metres, it's not even a tenth as deep as the deepest borehole.




Last Updated 22 November 2022

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