During 1938/39 there was a real fear by the authorities that if war broke out, bombing raids would cause mass casualties. Trenches were dug in parks to protect the public if they were caught out in a raid and couldn’t get to their own shelters.
Trenches were dug at right angles to each other, with earth walls reinforced with sandbags and a corrugated iron roof covered with a layer of soil. The roof was raised about a foot above ground level. They were not particularly safe. A direct hit or even a nearby bomb would probably collapse the whole shelter. They were also very unpleasant – smelly, unsanitary and waterlogged.
By October 1939 there were public shelters built or planned at The Oval, Penhill Park, Marlborough Park, Holly Oak Park and Willersley Park. The shelter at The Oval was designed for 316 people, but it immediately flooded and extra drainage had to be constructed. However, it seems no-one ever actually used the shelter during air raids. In Blackfen, people tended to have gardens with Anderson shelters (or if not, Morrison shelters), so they were much less likely to have to use public shelters in parks, unlike in London where most people didn’t have gardens. And most shelters dug in the ‘Black Fen’ were never going to be much use as they were often flooded.
As always, vandalism was a problem. There was damage and thefts from trenches in Holly Oak Park on 5 and 6 February 1940. Tools were stolen by five boys who were caught and charged, appearing in court on 20 February.
Today there is no trace on the surface of the trenches at The Oval. The entrance, which would have been in between the two rectangle sections, was blocked up.