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Met Office: How to count pollen

23 May 2012 Last updated at 00:04 BST

Patrick Sachon explains how the Met Office counts pollen, by heading to the roof and laboratories of King's College London.

He shows how the pollen is captured in a device called a Burkard trap and then taken to the laboratory where individual pollen grains are counted and ascribed to particular species, to produce data for national pollen forecasts.