Underground London - Ewell grotto

Ewell grotto is not underground and is rather tiny. But because it is called grotto I was curious to see it. It is located in the grounds of Ewell Court house, west of London. The house dates to the Edwardian period, 1870s.

It is known as The Fernery/Grotto.  It was part of a large conservatory attached to the house and was part of beautiful grounds designed by John Henry Bridges and landscaped by Pulhams of Broxbourne. The conservatory  was taken down at the start of World War 2

The inside of the grotto is made from pulhamite. Pulhamite was a patented anthropic rock material invented by James Pulham (1820–1898) of the firm James Pulham and Son of Broxbourne in Hertfordshire. This artificial material is constructed by bricks and rubble coated with cement. It creates natural looking rocks and crannies and enables ferns and orchids to grow on soil pockets. 

The grotto is built on a natural spring which formed part of the watering system. The little pool retains its level naturally. The interior was originally fed by a water system and there is evidence of artificial lighting.

The grotto was heated by a copper kettle boiler with pipe running outside and around to the greenhouse that currently houses the new tearoom. The dome/lantern on top of the grotto could be raised or lowered according to the temperature. This gave heat and steam to allow the ferns and orchids to grow. The hexagonal dome -

See more on The Grotto Directory which gives more info on the house. 

See also Historic England entry.