Croxley Green Station: You are looking for a small screw top container with logbook, pencil and room for small tradeables and a small TB or couple of Geocoins. Parking is available nearby opposite playground - from what I can tell there are no restrictions on this car park and it's open 24 hours.
It is possible to reach the tracks, bridge and place where the platform was, and people have been up to take photos, but there is a warning about trespassing so do this at your own risk.
There is no requirement to trespass in order to find this cache!
At time of publishing the cache contains a small FTF pinbadge prize, along with a sheep keyring, stickers, loaded dice and a small book (The Art of War - Sun Tzu)
Croxley Green Station
The station was opened in 1912 and was the last stop of the Watford and Rickmansworth Railway branches. The station was then 'temporarily' closed in 1996 and a section of the bridge removed to make way for an improved Ascot Road.
"Since 1991 the branch had been allowed to become increasingly run down in appearance and trains were infrequent and scheduled at inconvenient times, a process referred to by rail user groups as closure by stealth. This is because closing the station requires special powers. The minimum service required by law however is a once-monthly service, in one direction, which in this case, since 1996, is provided by "temporary" replacement buses. The station retains an active "live departure board" on the National Rail website and tickets to Croxley Green and Watford West are occasionally sold, which lead them to appear in the annual station usage statistics, from the analysis of which they are then deliberately excluded."
There are however, plans to close nearby Watford Tube station and re-use this line with a new tube station nearby at Ascot Road. The branch would then be extended to Watford Junction rail station. Whether this goes ahead is yet to be seen.
All across London and the suburbs there are a number of disused railways and tube stations along with partial or complete tracks and platforms with varying overgrowth of surrounding vegetation.
Some of these stations have been closed indefinitely, others have fallen into disuse through transport authorities negligent policies. But the fact that some of the signs and other furniture are still there even up to 50 years and beyond is fascinating.
Hopefully, a cache at these locations will help everyone to create an informal geocaching map of what the rail and tube network used to look like and perhaps make you wonder why they don't run trains in these locations anymore.
Wikipedia List of Disused Stations across London: Disused Railways Disused Underground Closed Underground Closed Railway Stations
Underground History - Someone who has the disused underground in great detail and provided lots of pictures.
Lost Lines - Croxley Green Branch - Photos.
Abandoned Tube Stations - More information and pictures.
Ghost Tube sign image generated with the help of London Underground Sign Generator and Gimp