ScienceDaily (Aug. 14, 2009) — London's oldest timber structure has been unearthed by archaeologists from Archaeology South-East (part of the Institute of Archaeology at University College London). It was found during the excavation of a prehistoric peat bog adjacent to Belmarsh Prison in Plumstead, Greenwich, in advance of the construction of a new prison building. Radiocarbon dating has shown the structure to be nearly 6,000 years old and it predates Stonehenge by more than 500 years.
I haven't seen this reported anywhere else, but to be honest I haven't looked yet.
It looks to be a trackway to make it easy to walk across the bog, there have been others found round the country but the way this reads this is the earliest found.