1935 - A single specimen was captured at Lots Road power station, situated on the River Thames.
1949 - A second specimen was found in Southfields Reservoir near Castleford, Yorkshire. This reservoir tops up the canal system and it is likely that the crab was introduced through shipping on the Humber River.
1973 - Three further specimens were collected from the River Thames at West Thurrock power station.
It isn't known why Britain didn't experience the same population explosion that swept through Europe in the 1930s.
The population of mitten crabs in the Thames continues to increase, and records from both Europe and China have shown that the entire Thames catchment is at risk of invasion. So far:
Map showing the distribution of mitten crabs reported in the Thames catchment from 27 August to 15 November 1996 PDF (83.7 KB)
Map showing the distribution of mitten crabs in the UK (dots indicate recorded sightings). © Crown copyright, Defra (MB0102)