False widow spiders - how dangerous are they?

A school has been closed because of an infestation of venomous false widow spiders, and experts say they are on the increase. But how much of a threat do they really pose?

Sightings of the false widow spider, said to be Britain's most venomous, are on the rise and they are spreading.

The species came to the UK in the 1870s and populations have grown since then.

But experts say the species is not usually aggressive towards humans and that being bitten is rare.