Holme Fen, specifically Holme Posts, is believed to be the lowest land point in Great Britain at 2.75 metres (9.0 ft) below sea level.
Before drainage, the fens contained many shallow lakes, of which Whittlesey Mere was one of the largest. The River Nene originally flowed through this mere, then south to Ugg Mere, before turning east towards the Ouse. By 1851, silting and peat expansion had reduced Whittlesey Mere to about 400 ha and only a metre deep. In that year the mere disappeared, when new drains carried waters to a pumping station and up into Bevill’s Leam. The drainage turned both the mere and the Holme Fen into usable farmland, but subsidence followed.
In anticipation of the ground subsidence, the landowner William Wells had an oak pile driven through the peat and firmly embedded in the underlying clay; he then cut the top level with the ground in 1851 and used it to monitor the peat subsidence. A few years later, the oak post was replaced by a cast iron column (reputedly from The Crystal Palace building at The Great Exhibition of 1851), that was similarly founded on timber piles driven into the stable clay, with its top at the same level as the original post. This is the Holme Post that survives today. As it was progressively exposed it became unstable, and steel guys were added in 1957, when a second iron post was also installed 6 m to the northeast. The post now rises 4 m above the ground, and provides an impressive record of the ground subsidence; both posts are standing today.
This picture comes the WDIDB Collection
