The above co-ordinates take you to Knockholt railway station. The station is on the South Eastern Main Line and is 16 miles 44 chains (26.6 km) down-line from London Charing Cross.
When the South Eastern Railway (SER) (a railway company in south-eastern England from 1836 until 1922) opened their "cut off" line through Orpington, Sevenoaks to Tonbridge in 1868, there was no station between Chelsfield and Dunton Green. It is understood that a Knockholt Vestry meeting in March 1871 resolved to request the SER to build a station for Knockholt. Eventually, the SER agreed to provide a station if a £3,000 contribution was provided by "local parties". This was raised and "Halstead for Knockholt" (the station being much closer to Halstead than Knockholt) was opened in 1876. The station name was changed to Knockholt in 1900 to avoid the confusion which had arisen with Halstead Station in Essex.
Author Edith Nesbit spent some of her adolescence in Halstead during the 1870s and her book The Railway Children is thought to be based on her time living in a house, Halstead Hall, whose garden is about a mile and a half from the railway line.
To locate the magnetic cache you need to go to
N51 20.(a+c)b(d-a), E00007.(e-b)(c-b)(d/b)
a=The number of the platform which takes trains to London.
bcd= The number of telegraph pole “DP bcd” located near the bus stop on the London Road, opposite the station approach.
e= The number of letters in the name of the former golf club in the immediate vicinity (walk up the road to some gates).
Be careful - this area can be busy.